If every Donald Trump voter again cast their ballot for Donald Trump in 2020, he could still fall short of victory — possibly devastatingly so.

Approximately 46 percent of Americans voted for Trump in 2016. That’s fewer than voted for Mitt Romney four years earlier and only slightly more than the 45.5 percent who voted for John McCain during his landslide defeat in 2008.

That Trump became president where Romney and McCain failed is a fascinating story of demographic alignments with the quirks of the Electoral College and the shifting dynamics of third-party candidates. But rather than focusing on the changes that allowed Trump to win where Romney lost, the media have instead become curiously hung up on the views of the not-especially-large minority of the public that voted for Trump.

I went back out and talked to the voters I interviewed before the election. Here's what I found #trump100days https://t.co/LUBfRaosAM — SalenaZito (@SalenaZito) April 23, 2017

The truth is, however, that all incumbent presidents retain the vast majority of their support. Herbert Hoover presided over the most disastrous term of office on record and still got 80 percent of his previous vote total during his obviously doomed reelection bid. Trump faced a divided opposition and the overwhelming presumption that he would lose.

The primary political question of 2018 and 2020 isn’t whether Trump’s voters will abandon him and the GOP, but whether Democrats will manage to field candidates and messages that inspire Trump’s critics to unite and vote for the same person. It’s not an impossible task, but it’s not a trivial one either.

To understand America’s political future, we need to know less about Trump’s supporters than about his opponents.

Three things “Trump voters” might mean

Roughly speaking, vague references to “Trump voters” tend to end up falling into one of three buckets:

Trump’s primary voters: These are the true Donald Trump fans. The people who decided to throw tradition to the wind and turn out and vote to nominate a person who didn’t have the basic attributes of a traditional presidential nominee. That amounts to about 14 million people who voted for him — only 45 percent of Republican Party primary voters.

The typical Trump voter: This is a very boring but numerically large group of people — basically Republicans. Most Republicans didn’t vote in the 2016 GOP primary, and most 2016 GOP primary voters didn’t vote for Trump. But most of these Republicans who weren’t especially enthusiastic about Trump did what they do every four years and voted for the GOP nominee, just as Hillary Clinton coasted to easy wins in states like Vermont and Washington where the primaries showed her to have few enthusiasts.

The marginal Trump voters: Typical Republican Party voters are a much larger group of people than swing voters who defected from the Democrats to vote for Trump. But winning the votes of people who always vote GOP isn’t enough to make you president. The converts were small in number, but they made the difference between winning and losing.

All these groups of people are interesting, but they are interesting and important for different reasons. In particular, while voters in category one and category two are easier to locate (because they’re more numerous), the kind of “Trump Country” reporting that unearths them is largely irrelevant for the purposes of political analysis. The United States is a gigantic country with 330 million residents and well over 100 million people who routinely vote in presidential elections. Even a candidate who loses badly is going to have a large base of core supporters.

Marginal Trump voters matter a lot more politically. Presumably some people voted for Barack Obama in part because he pledged to renegotiate NAFTA, were disappointed that he didn’t, voted for Trump because he pledged to renegotiate NAFTA, and may be disappointed when he doesn’t do it either.

Tracking these marginal voters makes sense, but it’s important to remember how small the margin really was. Fox News covered a Washington Post poll showing that 96 percent of Trump voters stand by their decision with the headline “No Regrets.” The fact is, however, that if 4 percent of Trump voters had stayed home rather than voting Trump, he would have lost Wisconsin, Michigan, Pennsylvania, and the White House.

Third parties made a big difference in 2016

While Trump got a smaller share of the vote than Romney, Gary Johnson and Jill Stein both massively improved on their 2012 showings. The result was that while Hillary Clinton did 3 percentage points worse than Barack Obama had done four years earlier, even as the GOP also lost ground.

Even though the total numbers involved aren’t huge, it’s important to not understate the scale of the third-party improvement. Evan McMullin in fifth place got a larger share of the vote in 2016 than Stein had gotten in fourth place in 2012. Stein’s level of support slightly more than tripled and so did Gary Johnson’s.

These third-party voters made a huge difference in the Electoral College. Trump didn’t improve on Romney’s overall performance, but his supporters are more efficiently sorted to win electoral votes, so he improved on Romney’s totals in Wisconsin, Michigan, and Pennsylvania. Still, he didn’t crack 50 percent in any of those states. He was also below 50 in North Carolina, Florida, and Arizona outside of the shattered blue wall. And thanks to McMullin’s strong Mormon support, he even fell far below 50 percent in Utah.

Yet despite third-party voters’ centrality to the outcome, we haven’t yet seen the cavalcade of loving profiles of “Johnson Country” asking what people who voted for neither Trump nor Clinton think. We know that the 2016 presidential election featured a highly unusual matchup between two nominees who were viewed negatively by most Americans. And we know that most voters assumed Clinton would win. The reaction of those who voted for neither to the realities of Trump-era governance is a more important political question than the reactions of Trump’s supporters.

We should pay attention to non-Trump voters

Trump is by no means the first president to take office without having secured a majority of the popular vote.

But Bill Clinton and George W. Bush both took office with strong overall approval ratings, indicating that many Americans who didn’t vote for the winner nevertheless were impressed by his outreach during the transition and early months of his presidency. Trump has governed with essentially zero effort at outreach — no token Democrat in his Cabinet, no reassuring words to those alarmed by his victory, and no effort to prioritize the elements of his agenda that have some cross-party appeal.

Trump’s inability to win over the majority of voters who backed a rival candidate is a much bigger deal than his skill at retaining the support of most of the people who already voted for him. The big question in American politics is whether Trump’s opponents can find a platform and set of candidates that unite the diverse and somewhat diffuse anti-Trump majority, not whether the president’s fans continue to celebrate him.