Sen. Joe Donnelly, the vulnerable Indiana Democrat, has been working the middle to survive this year's election. He's advertising about his own moderation. He votes with the president some days, votes against him others, and reminds voters of his centrist record every chance he gets. It is the only way to win re-election in a state that went for Trump by 19 points, and from day one it has been the de facto strategy of the Donnelly campaign.

Donnelly was just one of the three Senate Democrats who voted to confirm Neil Gorsuch to the Supreme Court. He was happy to do it because it solidified his reputation as a moderate while placating some conservatives. Suddenly, the incumbent wasn’t just another partisan swamp creature. He was an independent willing, to work with or split with the president, depending on the situation.

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Donnelly tried to run the same play with Brett Kavanaugh, appealing to his centrist credentials. He wouldn’t support Kavanaugh, he said, not because the nominee wasn’t qualified or of bad character, but because the FBI never had a chance to investigate allegations of sexual assault.

It was a decent excuse until Sen. Jeff Flake, R-Ariz., got the FBI to investigate. Donnelly suddenly had to change his explanation. He began to argue that Kavanaugh wasn’t qualified because of his “temperament and impartiality.”

That was good enough for Sen. Kamala Harris,D-Calif., the progressive superstar and presumed 2020 presidential contender who is now raising money on behalf of Donnelly and against Kavanaugh.

"I want you to know I am doing all I can to stop Kavanaugh from being confirmed this week — and I’m not alone in that fight,” Harris wrote in the email obtained by the Washington Examiner. “My colleague Joe Donnelly is in one of the closet (sic) re-election campaigns in the country.”

This confirms that Donnelly won't be changing his mind in favor of Kavanaugh. At the same time, the Harris endorsement makes it a lot harder for Donnelly to run as a moderate. She has long been auditioning for role of "hashtag-resistance" candidate. And Donnelly is with her now.