CNN  — 

The political world’s focus on the possible impeachment of President Donald Trump by the House has obscured a critical shift in the battle for control of the Senate: Democrats now have a genuine chance at retaking the majority come November 2020.

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“With President Donald Trump struggling to recreate his 2016 Electoral College victory, control of the Senate should be regarded as in play,” Nathan Gonzales, a non-partisan political handicapper and publisher of “Inside Elections,” said in his tipsheet. “Republicans are still more likely than not to maintain control of the Senate, but Democrats have a legitimate path to control, particularly if they win the White House.”

This is a big deal – for a number of reasons, not the least of which is that the Senate is tasked with confirming (or not) presidential picks for the Supreme Court. Trump was able to get two conservative justices through the Senate – Neil Gorsuch and Brett Kavanaugh– during his first term and, due to the advanced age of a number of the justices, there exists a very real possibility of several more openings on the nation’s highest court within the next few years.

Beyond that, a unified Democratic Congress – assuming Democrats keep control of the House – could be a massive boon for a newly elected Democratic president in 2021 or a major thorn in the side of Trump as he seeks to build a legislative legacy in his second term.

So why are Democrats now in a better position to make that scenario a reality? A combination of a continued decline in the national political environment for Trump coupled with strong fundraising numbers by a slew of Democratic challengers.

The 2020 map was always a bit of a challenge for Republicans. The party has to defend 23 seats next November as compared to just 12 for Democrats, the result of a 2014 election that delivered GOP wins across the Senate map. It’s never an easy road when you are defending almost twice as many seats as your opponents.

Those raw numbers, however, looked to be a bit deceiving. After all, there are only two states – Maine and Colorado – among those 23 that a) Hillary Clinton won in 2016 and b) Republican incumbents are running for reelection. And, while Democrats have relatively little to worry about among their 12 seats, they do have to try to reelect Sen. Doug Jones (D) in Alabama – a near-impossible task in a presidential election year.

Those developments – coupled with the fact that Senate Democrats need a net gain of three seats if their side wins the White House and four if they don’t – had led to a cementing of conventional wisdom over the past year that went something like this: Sure, it’s possible that Democrats can win, but it’s still a bit of a long shot.

Those odds have shortened in recent months.

In Colorado, Democrats convinced former Gov. John Hickenlooper to drop out of the 2020 presidential race and challenge Sen. Cory Gardner who was already among the most vulnerable GOP incumbents in the country.

In Arizona, astronaut Mark Kelly (D) has proven to be a dynamite fundraiser, ending September with $9.5 million in the bank – more than Joe Biden had on hand at the same time for his presidential bid. And Republicans continue to worry about Arizona Sen. Martha McSally’s (R) abilities as a candidate.

In Maine, Sen. Susan Collins (R) looks to be in for the most serious race of her two-plus decade career as former state House Speaker Sara Gideon reported raising more than $3 million dollars over the past three months – outpacing the incumbent by more than $1 million.

In North Carolina, Sen. Thom Tillis has to deal with a self-funder running to his right in the GOP primary and then the prospect of a race against a Democratic military veteran in a state that has become a genuine tossup.

And then there are a slew of other races in states – Georgia, Texas, Iowa – where Trump won by single-digits in 2016 and where Democratic challengers are likely to be well-funded enough to be in a position to capitalize if a) the national political environment goes even more south for Republicans or b) the GOP incumbents make a major mistake or slip-up between now and next November.

As Gonzales noted in his recent overview of the state of the Senate playing field:

“Individually, each of those races has its challenges, whether it be a strong incumbent, unproven Democratic candidates, or the political lean of the state. But when taken collectively, that Democrats need to win (or Republicans need to find a way to lose) less than 20 percent of those competitive contests, Democratic odds look much better.”

To be clear: Democrats are not favored to retake the Senate – particularly given the fact that Jones is a near-certain loser unless Republicans nominate Roy Moore (which they might do!). But the last few months have made clear that what once looked like a long-shot bid by Democrats for the Senate majority has turned into a much more plausible possibility.