Washington (CNN) Two things can -- and likely are -- true about the possibility of President Donald Trump facing a serious primary in 2020.

Why talk about 2020 today? Well, because Trump has already rolled out his 2020 slogan ("Keep America Great!"), has already hired a campaign manager for the contest and is in New Hampshire on Monday -- not an accident! -- to give a long awaited speech on the opioid crisis.

And because, Arizona Republican Sen. Jeff Flake is sounding more and more like a candidate these days.

"I hope that somebody does challenge the President," Flake said on CNN's "State of the Union" Sunday . "What I'm seeing is that there is a crying need out there for some Republicans to stand up and say, 'This is not normal, this is not right.'"

That sure sounds like someone who wants to run. Ditto Ohio Gov. John Kasich, who said on CNN earlier this month that "all options are on the table" when it comes to his political future.

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Chances are that either Flake or Kasich -- or maybe Flake AND Kasich -- run against Trump in 2020.

That would be a big deal, but probably not for the reason you think.

Neither Flake nor Kasich would have anything more than a puncher's chance -- at best -- against Trump unless something drastic happens (think Mueller investigation) between now and 2019.

Whether you like it or not, Trump's hostile takeover of the Republican Party during the 2016 primary fight is now virtually complete. His Twitter rants against respected individuals like Robert Mueller go largely unremarked upon by congressional Republicans. A tax plan that would add more than $1 trillion to the deficit? Congressional Republicans barely batted an eye! Trump's suspicion of trade deals? A-OK!

If you need to know how total the Trump takeover has been, look only as far as Flake. Flake was elected to the House and Senate from Arizona as a solidly conservative Republican and a deficit hawk.

But, during the course of the 2016 campaign, he became one of the leading voices of the anti-Trump movement within the GOP. Trump, to hear Flake tell it, was a total abandonment of Republican core principles. Flake believed so deeply in this idea that he wrote a book about it!

And, not surprisingly, he earned Trump's ire.

Tweeted Trump : "Sen. Jeff Flake(y), who is unelectable in the Great State of Arizona (quit race, anemic polls) was caught (purposely) on 'mike' saying bad things about your favorite President. He'll be a NO on tax cuts because his political career anyway is 'toast.'"

Flake actually voted for the tax cuts. But Trump was right that his career was toast. Flake's retirement announcement last fall came amid polling that showed he couldn't win a Republican primary -- due in large part to his critique on Trump.

Now. The Arizona Republican Party isn't the GOP electorate nationally. It has long been one of the most conservative in the country and was an early adopter of Trump's populist/nationalist messaging.

But, still.

The point here is that while there are clearly pockets of discontent within the Republican Party toward Trump -- Flake was warmly received in New Hampshire on Friday -- it's hard to see a broad-scale mutiny against the incumbent short of a bombshell finding about Trump in the Mueller investigation. (Possible but not probable.) If Republican leaders haven't walked away from Trump in any great numbers to date, why would they start doing so in 2019? (The answer, of course, is that they won't because GOP voters remain largely behind Trump.)

And now for the giant caveat. Which is that while neither Flake nor Kasich -- nor anyone else mentioned as a potential primary candidate in 2020 -- has much of a chance against Trump, if one of them runs and gains even a marginal amount of traction, it could well hamstring the President's re-election chances.

History is a helpful guide here. The last two sitting presidents to face real primary fights were George H.W. Bush in 1992 (Pat Buchanan) and Jimmy Carter in 1980 (Ted Kennedy). Neither Kennedy nor Buchanan won -- and only Kennedy actually had a chance to win. But Bush and Carter both went on to lose their re-election fights. That is not a coincidence.

There are both logistical and symbolic problems causes by a semi-serious primary challenge.

Logistical first. The President needs to spend money, time and organizational prowess on a primary fight. If Flake or Kasich ran, Trump would have to divert some chunk of cash -- and manpower -- that he'd like to reserve for the general election fight. Ignoring either of those men in a state like, say, New Hampshire, could have real world consequences

Symbolically, presidents always -- or almost always -- do better in the eyes of the public when they stay above the political fray for as long as possible. A primary challenge forces a president back into being just another politician far sooner than they would like to.

Then there is the fact that discontent toward Trump -- among Republicans -- remains somewhat amorphous at the moment. As in: Sure, there are a group of "never Trumpers" out there. But, right now, they lack any sort of cohesion. A candidate -- like Kasich or Flake -- who steps up and says "I will stand for you" suddenly allows that discontent to focus and to potentially grow. Putting a face to a feeling, having someone to believe in, makes all the difference in the world.

That connection not only makes it more likely for an anti-Trump message/coalition to exist but also improves the chances of the discontent toward Trump lingering well into the general election. That's what happened with Carter and Bush; long after Kennedy and Buchanan had conceded defeat, the people who backed their candidacies remained unenthused about the prospect of voting for their party's incumbent president.

All of which means that if Jeff Flake thinks he can topple Trump in a primary, he is sorely mistaken. But if he thinks he can weaken Trump and potentially rob the incumbent of four more years in office, he's not talking crazy.