WASHINGTON — With a flat-top haircut, three missing fingers and an impressive girth, Sen. Jon Tester has somehow kept a low profile in Congress. That’s until he caught the attention of Americans — and President Donald Trump — by airing startling allegations that toppled Veterans Affairs nominee Ronny Jackson.

It’s not necessarily the kind of high-stakes debut political strategists would dream up for Tester, a plain-spoken Montana Democrat running for re-election in a Trump-won state with more veterans per capita than almost any other. But the deed is done. Trump is responding. And now it’s game on in a midterm race that could help determine control of the Senate.

“I want to tell you that Jon Tester — I think this is going to cause him a lot of problems in his state,” Trump said Thursday on “Fox & Friends.”

Trump is still defending Jackson, the Navy rear admiral who served three presidents as a White House physician but withdrew from consideration for the VA position Thursday among allegations of drinking, overprescribing prescription drugs and fostering a hostile work environment.

Just as vigorously, Trump turned his sights on Tester, and is likely to swoop in to campaign against the senator. Trump’s twitter thumbs haven’t even engaged yet.

“Jon Tester has to have a big price to pay in Montana because I don’t think people in Montana — the admiral is the kind of person that they respect and admire and they don’t like seeing what’s happened to him,” Trump said.

For Tester, heading home for the weekend, he says he wouldn’t have done it any differently, believing it’s his duty as the top Democrat on the Senate Veterans Affairs Committee, to scrutinize the nominees and ensure the best person to head the troubled VA.

“We had a job to do and we did it,” Tester said.

The senator says he didn’t seek out the allegations, but that more than 20 military and retired military personnel brought concerns to the committee. It would have been a “dereliction of duty” not to investigate, he said. And even though the claims were not fully probed or proven true, he says it was important to bring them forward publicly for the sake of transparency.

“It’s about doing the best thing you can do to make sure you got a great country,” he said.

Tester’s happy to invite Trump to Montana for a look-see at the challenges in rural America. Montana is home to nearly 100,000 veterans, among a population of 1 million, and the president’s trade tariffs are worrying some farmers.

“I welcome him to come out any time and we’ll talk about the issues that are important to Montana,” Tester said. “I’ll continue to work with him when I can, and hold him accountable when I must.”

The Senate race in Montana will be among those watched this fall, part of a constellation of red-state contests where Republicans want to pick off Democrats to bolster their slim 51-49 majority.

Flipping the Montana seat may be easier on paper than practice. Sure, Trump won Montana by 20 percentage points in 2016 and remains popular in the state.

But unlike many other senators, Tester is running with a recognizable brand of his own, as a third-generation farmer near the little town of Big Sandy, a former teacher who started in politics on the school board. He hardly looks like he’s gone Washington.

It’s far from clear that the president’s attack will hurt the senator. Trump plucked Tester’s main rival, Ryan Zinke, from a potential race by tapping him for Interior Secretary, leaving several candidates scrambling for the GOP nomination.

They pounced on the opportunity to align with Trump against the two-term incumbent.

“He’s not a supporter of the president,” said one, Russ Fagg, a retired judge. “It’s an attempt to cozy up to a president who is popular in our state, and it’s disingenuous.”

Candidates Matt Rosendale, the state auditor, and Troy Downing, a businessman, also criticized Tester for his role in releasing what they called unsubstantiated claims against Jackson.

“Our view is this race gets more competitive by the week, and entirely because of what Tester is doing,” said Steven Law, the president at CEO at the Senate Leadership Fund, a super political action committee aligned with Senate Majority Leader Mitch McConnell, R-Ky.

Others though, say Trump’s attack could actually help. Tester needs independent voters, strong Democratic turnout and some Republican defections in November. It could showcase Tester’s independent streak and help with all three, said Montana State University political scientist David Parker.

Tester received an unexpected assist Thursday from an old ally, Chuck Hagel, the former Nebraska senator and Secretary of Defense, who was so outraged over Trump’s attack that he dialed up his distant colleague and offered to help campaign.

“What I heard this morning out of the president and others vilifying Tester, it made me sick,” Hagel, a Vietnam Veteran, told AP. “Jon Tester is as clear, direct, honest, transparent and pure on veterans matters as anyone I’ve ever run into.”

A Republican who has often sparred with his own party, Hagel said the GOP needs to stand up to Trump’s outbursts and “say enough is enough.”

“The good people of Montana,” he said, know enough about Tester “that they trust him.”

Tester, he said, has represented the state “in a way people of Montana can be proud of, they don’t have to hold their head in shame.”

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