Editor’s Note: Matt A. Mayer is president of Opportunity Ohio, a free market think tank, and long-time political commentator. The opinions expressed in this commentary are his own. View more opinion at CNN.

(CNN) —  

Does Ohio still matter in presidential elections? For years, both parties believed that winning the presidential election required winning Ohio. That belief faded for Democrats as Ohio’s population growth failed to keep up with that of the rest of the nation, which dropped Ohio’s electoral power from 25 votes in 1980 down to just 18 in 2020.

For Republicans, however, Ohio remains a state that its candidate must win to push past the 270 electoral vote. The primary reason for this reality is that so many of the other big electoral vote states like California (55 electoral votes), New York (29), Illinois (20), and New Jersey (14) are solidly blue. A Republican presidential candidate hasn’t won any of those states since George H.W. Bush won three of the four in 1988. Those four states give any Democratic candidate a huge starting base of 118 electoral votes.

The only reliably big red states for Republicans have been Texas (38) and Georgia (16) totaling 54 electoral votes. That large disparity in big state bases is why winning the White House is always a high stakes game for Republicans, as they must cobble together all of the small states forming the Republican “L” in the middle of the country, and the South and still grab a significant share of the battleground states. It is also why Democrats try to put Texas and Georgia in play.

In 2020, the battleground states include Florida (29), Pennsylvania (20), Michigan (16) and Wisconsin (10). Along with Ohio, Donald Trump won those four states in 2016, thereby securing the presidency with 304 Electoral Votes. A loss of any three of those five states makes winning in 2020 impossible for Trump.

Here’s why winning Ohio should be the easiest.

First, in the last 20 years, of the 38 non-judicial statewide elections, Republicans have won all but 10 races: Barack Obama in 2008 and 2012; Sherrod Brown in 2006, 2012 and 2018; and governor, attorney general, secretary of state, and treasurer in 2006, with Democrat Richard Cordray winning the attorney general special election in 2008. Obama won by less than 5% in 2008 and less than 2% in 2012. After his first big win in 2006, Brown’s next two US Senate wins were by about 6% each time, pushed to victory by Obama’s reelection effort and the Democratic waves in 2006 and 2018. The four state office wins in 2006 all occurred because of the massive anti-Bush wave of 2006.

Next, Trump beat Hillary Clinton by more than 8% in 2016. It wasn’t even close. Trump’s position on trade, nearly identical to Brown’s pro-worker position, allowed him to win blue collar union voters in the traditional blue Ohio counties that run from the northeast corner of the state down through Appalachia and over to Cincinnati. The same kind of voters went for Trump in Pennsylvania, Michigan and Wisconsin. Those Reagan/Trump voters aren’t likely to abandon Trump in 2020, especially after passage of the United States-Mexico-Canada trade agreement and the first phase agreement with China.

Finally, after the Great Recession hit Ohio harder than most other states, voters in key Democratic strongholds moved south and west, likely making it harder for Democratic candidates to run up the table in the big counties, as Republicans strung together large margins in all of the smaller red counties. In addition, African-American voters didn’t turn out for Clinton as they did for Obama. For example, in 2008, Obama won 458,422 votes in Cuyahoga County (Cleveland) with a colossal 258,542-vote margin over John McCain. In contrast, just eight years later in 2016, Clinton earned about 60,100 fewer votes than Obama had in 2008 in Cuyahoga County, while Trump received about 15,600 fewer votes than John McCain had won.

Though Ohio is much redder, the same dynamics are at play in Michigan, Pennsylvania, and Wisconsin, which is why Trump squeezed out surprise victories in those states in 2016.

The reality is the only things likely to stop Trump from winning the Midwest states are a national recession and the loss of support of enough suburban white women due to his caustic style. Though he likely still could survive those events if the Democratic candidate comes from the Progressive wing of the party, which remains an open question.

Given the highly partisan approach the Democrats have taken on their impeachment activities, polling by Gallup indicates that independents are moving towards Trump, which should hold true for independents in the Midwest. Those voters swung to the left in 2018 to deliver the US House to Democrats, but impeachment may push them back towards Trump in 2020.

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Fundamentally, Trump cannot win the presidency without winning the Midwest. As we enter what will be the craziest election year in modern history, all eyes increasingly will focus on four states that will decide who wins. Get ready for a wild ride!

An earlier version incorrectly described the number of swing states President Donald Trump cannot afford to lose in his bid for reelection.