WASHINGTON ― Vulnerable Senate Democrats are highlighting their work with their colleagues across the aisle and touting moments when they bucked President Joe Biden as they seek reelection in November.

In a new ad released this week, Sen. Jon Tester (Mont.), a red state Democrat that Republicans are hoping to oust in the battle for control of the Senate, played up his focus on protecting the U.S.-Mexico border, an issue that has ranked among the top most important problems in Americans’ minds.

“Jon Tester worked with Republicans, fighting to shut down the border, target fentanyl traffickers, and add hundreds of new border patrol agents. And he fought to stop President Biden from letting migrants stay in America,” said the narrator in Tester’s latest campaign ad, referring to his support for measures allowing border authorities to quickly expel migrants.

Tester’s seat is a top priority for Republicans, and with presumptive GOP presidential nominee Donald Trump’s popularity in Montana, he could face a very difficult path to reelection. The “flat-topped dirt farmer” is already facing millions of dollars in GOP ads criticizing his record on immigration, and Republicans are hoping to put added pressure on him to support an impeachment trial for Department of Homeland Security Secretary Alejandro Mayorkas next week, which most Democrats have rejected as baseless.

“We just want to set the record straight on what we’ve been doing on the border and not have some crooked goddamn dark money group not exactly telling the truth,” Tester told HuffPost when asked about the motivation behind his latest ad.

Meanwhile, Ohio Sen. Sherrod Brown, another vulnerable red-state Democrat, also released a new campaign spot this week that leaned into his work helping pass the CHIPS and Science Act, a bipartisan bill that boosted domestic high-tech manufacturing. The senator noted the funding from the bill supported a new factory with thousands of jobs in Ohio.

“I’m Sherrod Brown and I worked with Republicans to jump-start American chip manufacturing,” Brown said in his ad.

Ohio is another must-win state for Democrats if they want to retain control of the Senate. With Sen. Joe Manchin (D-W.Va.) retiring and his seat all but certain to flip to the GOP next year, Republicans will likely need to capture only two more seats to win the majority.

Democratic officials are hoping that by playing up their bipartisan bona fides, candidates from red states who are facing tough races can better appeal to voters ― a campaign strategy that has had mixed success in past elections.

“People in their states are very pragmatic and they know them as pragmatic senators who want to get things done, and the way to get things done is to find common ground,” Sen. Gary Peters (D-Mich.), the chair of the Democratic Senatorial Campaign Committee, told HuffPost.

But Sen. Steve Daines (R-Mont.), the chairman of the National Republican Senatorial Committee, said Tester’s maneuvering won’t matter.

“If I was a Democrat running in a state where I have voted with Joe Biden over 90 percent of the time, in a state where Trump’s going to win probably by 15 or 20 points, I’d be looking for something I could cling to for a bipartisan message,” Daines said of Tester, his fellow Montana colleague.

“But the reality is we voted very differently on virtually every major vote in the United States Senate,” he added.