Washington (CNN) President Donald Trump likes to boast that he is the most popular Republican president among Republicans that has ever existed.

"How do you impeach a president who has won perhaps the greatest election of all time, done nothing wrong (no Collusion with Russia, it was the Dems that Colluded), had the most successful first two years of any president, and is the most popular Republican in party history 93%?" he tweeted earlier this month

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That may be changing, at least according to a new Washington Post-ABC News poll that shows 1 in 3 Republican and Republican-leaning voters would like the GOP to nominate "someone other" than Trump in 2020.

That's a BIG number -- and speaks to the fact that there remains, at least in the broader Republican Party, a significant pocket of people who have simply never come around on Trump. People who don't believe that he represents the present or future of the GOP and are in search of some sort of alternative to him in 2020.

Who are these people? Largely who you would expect. Among those identifying as "liberal/moderate" Republicans, 49% want Trump to be renominated, while 48% want some other candidate to be the 2020 nominee. Among "very conservative" Republicans, 85% want to see Trump renominated while just 11% prefer another candidate. Overall, "conservatives" are more likely to want Trump to be renominated (74% Trump/23% someone else) than Republicans more broadly (65% Trump/32% someone else).

This Post-ABC poll comes at a very interesting moment in both Trump's presidency and the broader debate about the future direction of the Republican Party.

And external events continue to cloud Trump's political future. The arrest of his longtime associate Roger Stone on Friday and the expected release of special counsel Robert Mueller's report sometime in the next few months have served to highlight Trump's very real weaknesses heading into 2020.

Not coincidentally, there's been renewed talk of a serious Republican taking on the President in the 2020 primaries. While former Arizona Sen. Jeff Flake took himself out of consideration on Tuesday morning, there are still plenty of names mentioned, including former Ohio Gov. John Kasich, Nebraska Sen. Ben Sasse and, perhaps most intriguingly, Maryland Gov. Larry Hogan.

"Mr. Trump still commands the loyalty of a passionate electoral base that has rallied to him in trying moments, and advisers believe he will have room to right himself while Democratic presidential candidates are mired in a long nomination fight. Yet they are also growing anxious that he could face a draining primary of his own next year.

"Several prominent Trump antagonists are actively urging other Republicans to take on the president, and a popular governor, Larry Hogan of Maryland, has indicated he is newly open to their entreaties."

In his 2019 inauguration speech , Hogan cited his father -- a Republican congressman from Maryland who cast the lone Republican vote for all three articles of impeachment against Richard Nixon.

"Despite tremendous political pressure, he put aside partisanship and answered the demands of his conscience to do what he thought was the right thing for the nation that he loved," Hogan recalled.

Then, turning to his own work in Maryland, he offered this thought, which sounds a lot like a man thinking of running for a national office:

"While the tenor of today's national politics may have strayed from the noble example they set, I still believe that what unites us is greater than that which divides us. And to those who say our political system is too broken and can't be fixed, I would argue that we have already shown a better path forward. And if we can accomplish that here in Maryland, then there is no place in America where these very same principles cannot succeed."

Right? Eyebrows raised and all that?

I do think someone credible -- whether that someone is Hogan or Kasich or someone else I don't know -- runs against Trump in the 2020 GOP primaries. But even with the Post-ABC poll numbers in mind, that challenger is very, very unlikely to beat Trump.

Yes, there is resistance in some pockets of the GOP to the President. But the most conservative voters, who tend to make up the party's most committed base, are still very much behind Trump. As is the vast majority of the GOP infrastructure, which still means something -- particularly in a primary fight.

Simply put: There's a reason incumbent presidents just don't lose renomination all that often. And by "all that often," I mean that it has happened once -- ever. President Franklin Pierce lost his bid to be renominated as the Democratic choice for president in 1856 to James Buchanan. For all the focus on the 1980 primary fight between President Jimmy Carter and then Massachusetts Sen. Ted Kennedy, people sometimes forget that Carter, as embattled as he was, wound up winning renomination over Kennedy. (Want to read a GREAT book on that primary? Try Jon Ward's new one: " Camelot's End .")

Now, that's not to say there isn't real value for a Hogan or a Kasich to run -- even if their chances of victory are, um, not high. The danger for non-Trump Republicans is that the President destroys any semblance of what the party used to be before he became its leader. That when Trump leaves office -- whether in 2021 or 2025 -- there is no GOP outside of Trump.

Hogan, Kasich, and according to the Post-ABC poll, a decent number of other Republicans don't share Trump's view of the party or the country. And they have a vested interest in making sure that there is some Republican Party that has stood apart from Trump, so that when Trump is gone they can go to the public and say, "See, we all weren't -- and aren't -- like this!"

Running against Trump -- even in a likely quixotic primary -- could well preserve the idea of Republicanism apart from Trump for whenever Trump leaves office. And for whoever does decide to take up that anti-Trump mantle, he (or she) will likely be the first among equals in the presidential primary fight that follows Trump's departure from office.