Sen. Heidi Heitkamp, one of the most vulnerable Democrats up for re-election this fall, keeps piling up support from unusual places. First, it was praise from Donald Trump, who Senate Republicans are hoping will be the difference-maker in states he won two years ago, like Heitkamp’s home state of North Dakota. And now it’s coming from the Koch brothers, the conservative billionaires known for harnessing their dark-money network to elect Republicans.

Americans for Prosperity, a political advocacy group backed by Charles and David Koch, released a digital ad campaign late last week thanking Heitkamp for helping to pass legislation loosening some of the key provisions of the post-financial crisis banking rules known as Dodd-Frank. Heitkamp was one of about a dozen Senate Democrats who co-sponsored the bill, which was aimed at freeing up credit for rural areas and small businesses, but which also made it easier for banks to discriminate against black borrowers.

“Thank you, Sen. Heitkamp for giving Main Street relief,” reads the ad.

Heitkamp has made her willingness to work across the aisle central to her re-election pitch in North Dakota, which Trump won by 36 points in 2016. While Trump helped to recruit Republican Rep. Kevin Cramer to challenge Heitkamp, the president has nonetheless frustrated his fellow Republicans with his public affection for the Democratic incumbent, most recently on display when he signed the banking bill in the Oval Office last month.

The Kochs’ public thank-you note to a North Dakota Democrat is similarly odd, because of the importance of her seat, one of the GOP’s top pickup opportunities and one that will help decide control of the Senate next year. But the Kochs have occasionally taken a half-step away from strictly partisan politics, and they’ve made known some of their disagreements with Donald Trump. Earlier in the week, a trio of their groups attacked the president over the tariffs he’s imposed on China. And those same groups also recently had some kind words for another vulnerable Senate Democrat, Sen. Joe Donnelly of Indiana, for his support of “right to try” legislation allowing seriously ill patients to try unproven experimental treatments. Trump offered similar praise for Donnelly last week, just a few weeks after lambasting him at a campaign stop.

It’s not clear exactly how much cash Americans for Prosperity put behind the digital ad praising Heitkamp, but it’s almost certainly only a tiny fraction of the roughly $450,000 the group says it spent earlier this year on a TV and digital campaign attacking Heitkamp for her vote against the GOP tax law. Likewise, the new digital campaign is likely a rounding error for a network that has vowed to spend nearly $400 million during the midterms, the vast majority of which will be used to help Republicans in their quest to retain control of both chambers of Congress.