Democratic Sen. Jon Tester and Republican challenger Tim Sheehy squared off in Montana’s first Senate debate on Sunday — an early showdown in one of the most important races to determine control of the Senate next year.

The debate, sponsored by the Montana Broadcasters Association, offered a preview of how Democratic candidates campaigning in largely Republican states, like Tester, are navigating the task of sharing the ballot with President Joe Biden, who lost Montana by more than 16 points in 2020. While Tester sought distance from the Democratic president, Sheehy tried to tie him and Biden together.

“Some of the regulations that have come out of the Biden administration on energy are totally unacceptable,” Tester said Sunday morning, criticizing the Biden administration’s environmental regulations. “I pushed back on those regulations, and currently, I’m pushing back on regulations that the EPA has put out that wants to shut down a coal plant.”

“The bottom line is, he doesn’t listen to me enough,” Tester said of his relationship with Biden.

Asked about Biden’s new executive action aimed at curbing migrant border crossings, Tester again found fault with Biden.

“The president put out some executive orders [that] should have been done years ago, quite frankly,” said Tester of the Biden administration’s recent moves on the border.

Sheehy said Tester had voted with Biden most of the time and dug in on specific issues. On the issue of border security, Sheehy said, “Time and time again, Joe Biden and Senate Democrats, including Jon Tester, have had the opportunity to shut down that border and pass legislation to do so.” Sheehy later went on to dismiss Biden’s recent executive action as “political theater.”

Sheehy, a former Navy SEAL and entrepreneur, also tied Tester to Biden on military issues.

“Jon Tester’s chairmanship of the Defense Appropriations Committee and Joe Biden’s stewardship in the White House has led to the lowest military readiness in a generation,” said Sheehy.

“We focused on DEI and ESG in our military instead of making sure we are training warfighters,” Sheehy added. The Republican said earlier that watching the American withdrawal from Afghanistan in 2021 was a motivating factor for his Senate bid.

Republicans need a net gain of two Senate seats to guarantee a majority next year, or one seat plus the tie-breaking vice presidency. And Democrats are defending three seats in states Trump won comfortably in 2020.

Democratic Sen. Joe Manchin’s retirement in West Virginia has left it wide open for a GOP gain, and Tester’s race and Democratic Sen. Sherrod Brown’s in Ohio are two more prime targets for Republicans. Brown is facing a similar red-state dynamic against Trump-backed Republican Bernie Moreno in his state — not only trying to convince constituents to cross party lines but managing the Democratic president’s low favorability numbers in his state.

This article was originally published on NBCNews.com