Lisa Murkowski hasn’t even officially begun her 2022 re-election campaign, and she has already picked up a big endorsement — and a Democratic one at that, albeit a Democrat popular in GOP circles at the moment. In a joint interview with Politico, Joe Manchin declared that he would campaign for Murkowski “in a heartbeat,” hailing her efforts to work across the aisle to get the best deal for Alaskans. It’s a repeat of Manchin’s surprising efforts for Susan Collins last year, and perhaps a warning to fellow Democrats to lay off:

But Manchin doesn’t want to see his friend Murkowski defeated by a Trump-endorsed Republican — or a Democrat. He told POLITICO’s Playbook Deep Dive podcast that he will support Murkowski’s challenging reelection campaign in 2022 “in a heartbeat.”

“I’ve met a lot of good people in Alaska, they know when they’ve got the real deal. And they see the person that basically is bringing both sides together, trying to look for the best interest,” Manchin said of Murkowski in a rare joint interview. “People understand that they have a person that understands Alaska and has Alaska in her blood and in every part of her veins and every morsel of her body.”

Murkowski hasn’t officially launched her reelection campaign but was elated to get Democratic backing: “I would welcome his endorsement.”

Murkowski doesn’t have much to fear from Democrats anyway, and Manchin’s unlikely to step on Chuck Schumer’s toes as much with this announcement as he did in supporting Collins. Schumer’s not likely to invest much effort in fielding a candidate in Alaska, even if Trump-supported Kelly Tshibaka ends up with the official Republican endorsement. Murkowski won in 2010 through a write-in campaign that ended up humbling both the GOP and Democrats, staving off a Tea Party challenge in the primaries.

Manchin’s support this time might make another grassroots challenge moot anyway. After that election, Alaska went to an all-in nonpartisan primary where the top four vote-getters move to the general election, regardless of political affiliation. That means Murkowski will draw across the entire electorate rather than just GOP voters, blunting the effect of grassroots activists in determining access to the general-election ballot. It also ensures that Murkowski will have three other challengers in November 2022 rather than one or two, splitting whatever anti-Murkowski vote there might be.

Right now, Republicans need Manchin badly this session to keep the filibuster in place and reconciliation from becoming its back door. They can’t afford to take potshots at him in the midterms, and in fact will be likely to promote Manchin repeatedly as a reasonable Democrat to succor favor from him. That will make Manchin all the more valuable to Murkowski in Alaska, and at the same time a poison pill for Democrats tempted to invest heavily in a challenger. In a four-way race with Murkowski, Tshibaka, a Schumer-approved challenger, and a fourth candidate of any stripe, Murkowski can be expected to coast to victory, especially with Manchin’s help.

Murkowski would likely have coasted to victory even without Manchin’s help. The bigger problem for Republicans will come in 2024, when they hope to challenge Manchin in his deeply red West Virginia, where Joe Biden failed to win even a single county last November. Collins and Murkowski will undoubtedly return the favor by campaigning for Manchin, denying Mitch McConnell a flipping opportunity too. Maybe by that time, McConnell can convince Manchin to cross the aisle … if Schumer doesn’t force Manchin to do it first.