PHOTO: Gerald Herbert/AP
(CNN) —  

There’s a political dynamic that virtually guarantees Congress will remain locked in a contentious stalemate over gun violence like the weekend’s mass shooting in Texas and the risk of climate change embodied in the ferocious Hurricane Dorian menacing the Southeast United States.

Both issues highlight the effective veto over legislation that the Senate provides to a group of inland states – many of them smaller, preponderantly white and heavily rural – with deep ties to the fossil fuel industry and a strong gun culture.

These states – primarily across the South, the Plains and the Mountain West – provide Republicans enough Senate seats to sustain a filibuster blocking action on guns or climate change, despite polls showing that a clear national majority now supports a federal response to both.

Even if Democrats in 2020 hold the House, retake the White House and regain a Senate majority, this regional dynamic virtually guarantees Republicans could still block any legislation that offers an ambitious response to either challenge.

That’s why a growing number of Democratic observers think if the party regains unified control of government in 2020, climate and gun control will likely be the two issues that create the most pressure for eliminating the filibuster, which requires 60 votes to advance legislation in the Senate.

On both issues, a stark regional divide with cultural and economic implications now separates the parties.

Carbon emissions and gun ownership

Republicans hold a strong majority of Senate seats from states where the highest share of the population owns guns. They control even more of the Senate seats from the states most tightly tied to the fossil fuel economy, as measured by the share of carbon emitted in each state per dollar of economic output, according to federal figures.

A preponderant majority of the states at the top of both of those lists also voted for President Donald Trump in 2016. The states with fewer gun owners and lower carbon emissions per dollar of economic activity mostly backed Hillary Clinton in 2016 and largely send Democrats to the Senate.

To a large extent the rankings of the states on gun ownership and carbon emissions overlap. So do listings of the states on their exposure to other measures of social and economic change, like the share of the workforce in information-age digital jobs or the percentage of immigrants in the population.

As I’ve written before, this means Republicans now rely primarily on the states and voters least touched by – and most skeptical of – the demographic, social and economic changes remaking America in the 21st century, while Democrats have grown more reliant on the places and voters most welcoming of those changes.

That core divide between the parties has created a dynamic in which most Republicans in Congress feel comfortable ignoring what polls show is a clear national majority for action on guns and a growing consensus for a federal response to climate change – which will be the subject of a CNN town hall with 10 of the Democratic presidential candidates on Wednesday night.

Consider guns. Polls have consistently shown about 90% of Americans support requiring universal background checks on gun sales, including those at gun shows or across the internet. That figure includes nearly 90% of Republicans and gun owners.

A ban on assault weapons remains more controversial, but amid the relentless pulse of mass shootings over the past few years, about three-fifths of Americans are now expressing support for such a prohibition.

A Quinnipiac University poll last week even found that four-fifths of Americans support a requirement that all gun owners obtain licenses and nearly half support a mandatory buyback of all assault weapons now in circulation – two ideas considered at the far frontier of gun control policy that some of the 2020 Democratic presidential candidates are promoting.

2018 election changed the House

For years, a geographic mismatch in the House prevented this national sentiment from translating into policy. Many House Republicans held suburban seats in major metropolitan areas where support for gun control has grown in recent years, but still voted with their party and the National Rifle Association to oppose it. Last November, though, gun control advocates beat 40 Republican incumbents with high ratings from the NRA.

That created a clear urban-suburban majority for action on guns in the House: Earlier this year the House passed a universal background check bill with all but two voting Democrats supporting the measure. That stood in stark contrast to the 1990s, when the Democrats still held a large number of rural and blue-collar districts and 69 House Democrats voted against the Brady bill establishing the background check system for purchases at gun stores.

Now the House is weighing legislation to ban high-capacity ammunition magazines and, more gingerly, considering whether to push to pass a ban on assault weapons as well. Any of those votes would be close, but the modern metropolitan-based Democratic Party is in a far stronger position to muster a majority for gun control today than at any point in its history, since it relies far less than in the past on rural, Southern and blue collar districts.

But the geographic dynamics in the Senate virtually guarantee failure for all of these measures. That’s because states with high levels of gun ownership have elected more than enough Republicans to sustain a filibuster against any significant gun control measure. And even though polls show that most gun owners support ideas such as the universal background check and gun licensing (though not the assault ban), in those states elected officials have made clear they worry most about the response of the NRA and other segments of organized gun owners hostile to restrictions.

The tilt of states with high levels of gun ownership toward the GOP is dramatic. One academic study in 2015 that calculated the level of gun ownership in each state found in 19 states, 35% or more of the population owns firearms. Republicans now hold 27 of the 38 Senate seats from those states, and Trump won 15 of them. (The principal blue exceptions in the high-gun-owning states are Nevada, New Mexico, Minnesota and, unexpectedly, Hawaii.)

In another 10 states, the study found, between 30% and 35% of the population owns guns. Republicans hold 17 of their 20 Senate seats and Trump won nine of them. (Colorado was the only state in this grouping that backed Clinton.)

In the remaining 21 states, less than 30% of the population owns guns, the study found. Democrats hold 33 of their 42 Senate seats and just six of those states voted for Trump. (These exceptions comprised the closely fought swing states of Pennsylvania and Michigan, as well as GOP-leaning North Carolina and Ohio, and reliably Republican Missouri and Nebraska.)

The 21 states with the lowest gun ownership have more than twice the population of the 19 states with the highest levels. The low-gun states even have 30 million more residents than all 29 states where gun ownership exceeds 30%.

But the 44 GOP senators from the highest gun-owning states have more than enough votes to indefinitely sustain a filibuster against any expansive gun control measure, regardless of national public opinion on the issue.

’Concerned believers’ on climate change rising

The massive threat of Hurricane Dorian illuminates how the same dynamic governs climate policy. Scientists say while climate change does not increase the number of hurricanes, warmer temperatures in the air and water increase the likelihood more of the hurricanes that develop will become high-intensity storms with heavier winds and rain. “In other words, climate change makes it more likely for hurricanes to reach Categories 4 and 5 – and more likely for catastrophic damage to occur,” climate scientist Kristina Dahl of the Union of Concerned Scientists wrote last weekend.

Dorian, which has produced some of the heaviest winds on record, is passing over Atlantic Ocean waters that are about 1 degree warmer than in the past, Dahl reported. Rising sea levels also increase the risk of towering storm surges that can inundate coastal areas.

On climate change, public opinion has not coalesced behind a demand for action as clearly as on gun policy. But even so, in recent Gallup polling, two-thirds of Americans said they believed human activities were causing the climate to change and three-fifths said they believed the effects of climate change have already begun. Gallup said for the first time a majority of Americans qualified as what they called “concerned believers” who are convinced climate change is occurring and that it will pose a serious threat in their lifetime.

In another Gallup survey last spring, a solid three-fifths majority of Americans said they favored “proposals to dramatically reduce the use of fossil fuels such as gas, oil and coal” to lower carbon emissions. That number rose to nearly 7 in 10 among college graduates and nearly 8 in 10 among adults younger than 34, Gallup found.

As on guns, the evolution in the Democratic coalition that has reduced its reliance on rural and blue-collar voters, and shifted its center toward metropolitan areas, has made it easier for the party to reach consensus on climate issues. Earlier this year, the House passed legislation pressing the US to rejoin the international Paris climate accord, which Trump has announced his intention to leave.

All the Democratic presidential candidates have offered ambitious plans to transition the economy toward less reliance on fossil fuels – though there remains disagreement on whether to proceed as far and as fast as the “Green New Deal” proposed by Rep. Alexandria Ocasio-Cortez of New York and others.

Yet whatever Democrats can pass through the House, now or in the future, they face the impregnable resistance of what I’ve called “the brown blockade” in the Senate. As with gun ownership, the states that are most tightly tied to the fossil fuel economy have created a Republican phalanx in the Senate sufficient to block any meaningful action on climate through the filibuster.

The federal government measures the “carbon intensity” of each state by calculating the amount of carbon it emits for each dollar of economic output. The states on the upper end of this scale are those that either produce large amounts of fossil fuels or to a lesser extent, consume them to fuel manufacturing and agriculture.

In the 20 states that emit the most carbon per dollar of economic activity, all of them between the two coasts, Republicans hold 35 of the 40 Senate seats. Just the GOP’s additional six senators from the next five highest-ranking states give them enough votes to sustain a filibuster against climate action. Fully 47 of the 53 Republican senators represent the 30 states that rank highest in “carbon intensity.” Trump won 27 of those 30 states.

By contrast, Clinton carried 17 of the 20 states with the lowest levels of carbon emissions per dollar of economic output. (Georgia, Florida and North Carolina were the exceptions.) And those states, centered along the East and West coasts, have elected Democrats to 34 of their 40 Senate seats.

Those bottom 20 states in carbon emissions represent 53% of the national population, but the Constitution’s two-senators-per-state rule, magnified by the leverage of the filibuster, provides an effective veto on climate policy to the states most tightly bound to the fossil fuel economy, even though they constitute a minority of the population.

Filibuster a pivotal factor

The debates over guns and climate largely align the same states against each other. At least 30% of the population owns guns in 18 of the 20 states that emit the most carbon per dollar of economic activity. Viewed from the other direction, 13 of the 19 states with the very highest levels of gun ownership (35% or more) also rank in the top 20 for per-dollar carbon emissions.

The 13 states ranking near the top of both those lists are predominantly interior states with big energy and/or manufacturing industries, including Wyoming, Montana and North Dakota in the Northern tier; Louisiana, Arkansas, Alabama and Mississippi in the South; and West Virginia and Kentucky among the border states.

Conversely, 15 of the 21 states where less than 30% of the population owns guns also rank in the bottom 20 for carbon emissions per dollar of economic activity. The states low on both lists are mostly coastal states that have transitioned substantially to the information economy and have shifted their electricity generation more toward renewable sources and natural gas. They include California, Oregon and Washington along the West Coast, and along the East Coast, all of New England (except Maine), New York, New Jersey, Maryland and Virginia, as well as Illinois in the Midwest. (North Carolina is the state on both lists that leans most toward the GOP.)

Guns and climate are two of the issues where the priorities and inclinations of these distinct Americas collide most explosively. It’s possible the sheer magnitude of the damage from both gun violence and climate change could shift the balance toward action in some of the states that now mostly elect officials resistant to it, such as those at greatest risk for hurricane damage, like Florida, North Carolina and Texas.

It’s more likely over the near term that no matter how many mass shootings or hurricanes rattle the nation a unified consensus won’t emerge on how to respond. These issues loom as two of the principal arenas in which the battle for control of the nation’s direction will unfold between what America has been and what it is becoming. And the pivotal factor in that struggle may be whether the Senate filibuster survives the next time Democrats achieve unified control of Washington, in 2020 or beyond.