Republicans have an excellent opportunity to pick up seats in the Senate, with Democrats facing the daunting task of defending 26 seats in the upcoming midterms to nine for the GOP. North Dakota’s Heidi Heitkamp might be among the most endangered, defending a seat in a state Donald Trump won by 35 points two years earlier. The White House even got the challenger they wanted in Kevin Cramer, elected statewide three times to North Dakota’s only seat in the House.

So why, Cramer wonders, is Donald Trump publicly going easy on Heitkamp and not doing much to promote his candidacy?

President Trump is aggressively campaigning for Republican Senate candidates around the country and belittling their Democratic ­rivals, with one notable exception — Sen. Heidi Heitkamp of North Dakota.

Trump’s affinity for Heitkamp, who got a shout-out and a handshake at a recent White House bill signing, has frustrated top Republicans who see winning her Democratic seat as crucial to holding onto their fragile 51-to-49 majority. No one has felt it more acutely than GOP Rep. Kevin Cramer, whom Trump personally recruited to run against Heitkamp. …

Cramer says he believes Trump is giving Heitkamp preferential treatment because she is a woman. He accused the first-term senator of being insecure and going out of her way to stand near Trump at last month’s signing of the banking bill, which Cramer also attended.

“Have you ever watched the video? It’s obscene,” said Cramer, who in an interview with The Washington Post re-created Heitkamp’s movements and the setup of the room.

It’s all the more puzzling because of Cramer’s status as an early Trump supporter in 2016. He was among the first in Congress to endorse Trump, and earned enough credibility with Trump to get short-listed for a Cabinet position (Energy, which eventually went to Rick Perry.) Recruiting Cramer means he’s giving up an easy re-election bid to the House to take on Heitkamp, which should prompt an even more aggressive campaign to make sure that sacrifice pays off. What gives?

No one knows, it seems. As the Washington Post notes, Cramer’s preferred analysis falls pretty short. Trump proved repeatedly during the presidential campaign that he felt no particular compunction about playing hardball with female competitors, first with Carly Fiorina and then more famously with Hillary Clinton. (Or, for that matter, Megyn Kelly.) Trump and the White House have hammered Claire McCaskill in Missouri in this cycle. Whatever the reason for the kid-gloves treatment of Heitkamp, a gender explanation doesn’t fit at all.

One complicating factor is that Heitkamp has been of use to Trump at times, especially on nominations of controversial appointees like Gina Haspel at the CIA and Mike Pompeo at State. However, she’s hardly the only useful Senate Democrat running for re-election in this cycle.  Indiana’s Joe Donnelly voted for both Haspel and Pompeo, and has earned the epithet “Sleeping Joe” from Trump in this year’s Senate midterms. Joe Manchin voted for Pompeo and Haspel too, and no one thinks Trump will let Manchin off the hook.

The situation puzzles Say Anything’s Rob Port in North Dakota, who sees Trump’s lack of attention as a serious snub, even if no one can figure out what’s behind it. A Trump visit to Minnesota next week without any plans to stop by and help out Cramer makes it look even worse, Port writes:

Right now, with Democrats heavily invested in their Heidi-is-pro-Trump narrative, would be the perfect time for Trump himself to descend on the race and rile up the Republican base for Cramer. Only, that doesn’t seem to be in the works any time soon.

I reached out to the Cramer campaign for an update. “What I know at this point is we do not have a schedule for a Trump visit,” Tim Rasmussen, campaign spokesman, told me. “We hope he’s going to come. We have every indication that he will, but as of right now I’m not aware of a specific date in time.”

Maybe all is well behind the scenes. Maybe there’s no fire behind all this smoke.

But, barring some announcement for a North Dakota visit shortly, this sure looks like a snub.

Cramer’s campaign manager later told Port that the dates “didn’t work for Cramer,” but that’s a strange excuse. It sounds as though the campaign wants to de-escalate after Cramer openly attacked Mark Short for his friendliness with Heitkamp, perhaps hoping to get Trump back on board. Until that happens, though, no one’s apparently clear on why Trump isn’t more assertively supporting his own recruit in a race that Republicans should win handily — assuming they can get organized behind their chosen candidate. If they lose this slam-dunk and control of the Senate as a result, there will be enough regrets to stretch easily from one end of Pennsylvania Avenue to the other.