It was no accident that Sen. Jon Tester of Montana wound up on the campaign trail this week with the leader of Planned Parenthood’s national political action committee.

The endangered Senate Democrat, who’s running a tricky campaign that could determine whether Democrats keep control of the upper chamber, is leaning into abortion rights in a red state that most people do not associate with reproductive freedom or Democrats who can win statewide.

But Tester’s move is a sign of how abortion rights are at the center of the Democratic Party’s plan to cling to its one-seat Senate majority in November. In Montana and Florida, Democrats are betting that abortion ballot measures drive turnout among independent and left-leaning voters. They’re also hoping that Republicans are tempted to cross party lines for candidates who staunchly oppose a national abortion ban, which Democrats are warning is on the table if they lose control of the Senate.

That means not only talking up their own support for abortion rights — as Tester’s doing — but pointing out their opponents’ more extreme and slippery positions on the procedure that are generally out of step with many Americans.

“All of [the GOP] candidates have very strict positions on abortion,” Sen. Gary Peters (D-Mich.), the chairman of the Democratic Senatorial Campaign Committee, told reporters at the Democratic National Convention last month.

Tester, for example, has hammered his GOP opponent Tim Sheehy, the CEO of an aerial firefighting company, on abortion, claiming that Sheehy’s opposition to the procedure means he’d support a national abortion ban — which Sheehy has not directly come out in favor of, despite describing himself as “proudly pro-life” and calling abortion a “terrible, terrible thing” that he would like to “end tomorrow.”

A Democratic Senate majority hinges on winning a Senate race in one of three states that former President Donald Trump will likely also carry: Montana, Texas or Florida.

Democrats still view Montana as their best shot, even though a new AARP poll of the race had Tester trailing Sheehy by 6 percentage points in a head-to-head, a blow that resulted in one prominent election forecaster changing their rating from “toss-up” to “leans Republican.”

Both Tester and former Florida Rep. Debbie Mucarsel-Powell are hoping that abortion rights measures propel turnout, while Rep. Colin Allred is counting on backlash to Texas’ ultra-strict abortion law to give him a shot at ousting Republican Sen. Ted Cruz.

Those bets may backfire. In recent elections, voters in conservative states have happily backed liberal referendums like minimum wage hikes (Missouri) or restoring voting rights for felons (Florida) — and then cast ballots for Republicans who oppose those ideas.

Patrick Toomey, a pollster at Benenson Strategy Group, said ballot measures historically have not impacted individual candidates, but suggested reproductive freedom may be in a category of its own.

“Abortion is a little bit different than some of the other topics, and that may be a place where we see some shifts. I think one is around turnout, and [the other] is around the ability to force Republicans to get on the record about abortion, not just as a topic nationally, but in their state,” Toomey said at a DNC panel.

For Montana to pass its constitutional amendment enshrining abortion rights, some percentage of Republicans will need to support it, and Democrats will also need to show up in force at the ballot box.

Tester backs the measure, known as CI-128, while Sheehy has come out against it. The amendment seeks to enshrine a 1999 Montana Supreme Court decision that prevents the government from interfering in an abortion before fetal viability at 24 to 26 weeks. Abortion in Montana is currently legal up to that point.

A 2023 survey from a Montana-based progressive strategy firm found 60% of voters support either mostly legal abortion or abortion with some restrictions. But the survey didn’t account for political party affiliation or give clues as to how those responses would impact voter behavior at the ballot box. The findings tracked with a Pew Research survey from over a decade ago that found 56% of Montanans supported legal abortion in most forms.

Sheehy did not respond to a request for comment. In a statement to HuffPost, Tester spokesperson Monica Robinson said, “Sheehy knows he’s on the wrong side of this issue in Montana, where voters want less government intrusion in our lives — not more.”

Tester, highlighting one of his stops with Planned Parenthood, also cited Montana’s independent streak as a justification for his hands-off approach to reproductive rights.

“If there’s one thing that makes you a Montanan, it’s your love of freedom. You don’t want a politician, or a bureaucrat, or a judge, telling you — especially if you’re a woman — what health care decisions you’re gonna make,” Tester said. “Roe v. Wade being overturned was the biggest reduction of freedom in my lifetime, and yours, too.”

Montanans Securing Reproductive Rights, the coalition behind the ballot measure, stressed they’re promoting their cause without consideration of party affiliation. In a statement, they declined to mention Tester, the only statewide elected Democrat and the only statewide official who’s come out in support of the C1-128.

“We’ve seen incredible excitement and energy among Montanans about this initiative,” said Ashley All, a spokesperson for the group. “Reproductive rights and abortion are nonpartisan.”

But Planned Parenthood Action Fund President Alexis McGill Johnson, who appeared with Tester in Bozeman and Missoula this week, praised Tester and blasted his opponent by name.

McGill Johnson called Tester “one of the most effective senators in Congress with a proven record of support for reproductive health care access to boot. His opponent Tim Sheehy has vowed to be an opponent of reproductive freedom, and Planned Parenthood Action Fund will do everything in our power to keep him out of the Senate.”