(CNN) Maryland Gov. Larry Hogan is thinking about challenging President Donald Trump in the 2020 Republican presidential primary for one simple reason: He's not sure Trump can actually win a second term.

"The issue I'm concerned about is he has a very low re-elect number, I think in the 30s, high 30s, low 40s," Hogan said in an interview with CBS News' Ed O'Keefe . "So the chance of him losing a general election are pretty good. I'm not saying he couldn't win, but he's pretty weak in the general election."

Hogan's analysis is, on one level, obviously self-serving. If you want to challenge a sitting president in a primary (and Hogan is at least interested in the prospect), the worst thing you can do is suggest your motivation is selfish. The way to sell it to voters is that you aren't running because you have some deep-seated desire to be president -- although of course you do -- but rather because you are worried about the broader party losing its grip on power.

But regardless of the motivations behind Hogan's assessment of Trump as "weak," there's a larger question here: Is Hogan right? Is Trump ripe for the picking by any Democrat who wins the nomination next year? And, most importantly, is Trump so damaged that he simply cannot win re-election -- meaning that nominating him is a sure loser?

Obviously, any attempt to peer 20+ months into the future has to come with this caveat before we even start: Stuff -- ahem -- happens. Races for president are evolving creatures. They are impacted by outside events -- and how candidates react to them. Chance/luck plays a role. So there's that.

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