Manchin already signed on to two separate bills that would freeze the Iranian cash that’s set to unlock after a hostage swap with the country, and Brown and Tester are considering joining him. Brown said both Biden and former President Donald Trump “have failed to secure the border well enough,” comments that both Manchin and Tester agreed with.

“The prisoner swap, the $6 billion, I never was for that,” said Manchin, who has not yet announced plans to run for reelection. But he had a warning for his colleagues: “If Democrats don’t get serious about border security, they’re screwed. They’re screwing themselves.”

What’s more, Biden’s persistently low polling numbers give those senators — as well as the next tier of Democratic incumbents from purple states — plenty of room to stake out their differences with the administration. Independent Sen. Kyrsten Sinema of Arizona is making similar public and private moves, as she mulls another run.

Battleground Democrats breaking with Biden isn’t exactly a new phenomenon. Several Democrats up for reelection last cycle, like Sens. Maggie Hassan of New Hampshire and Mark Kelly of Arizona, strategically distanced themselves from Biden and the rest of the party. But it’s an even trickier balance for the three red-state Democrats up this cycle, given more difficult election prospects and the narrow Senate majority.

In a signal that party leaders are giving their members space, Democratic Senatorial Campaign Chair Gary Peters (D-Mich.) said senators “are going to do what they think is right.”

Red-state Democrats regularly break with presidents of their own party, though Democrats’ Senate map is particularly difficult this cycle. In a statement, White House spokesman Andrew Bates said, “President Biden and Senate Democrats from every corner of the party have built an historic record together despite one of the narrowest majorities in history,” citing efforts to lower drug costs and a new gun safety law.

There could be ample opportunities for these Democrats to make good on their rhetoric, though the party’s more centrist members face a tough squeeze between the president of their own party and conservative-leaning voters who will determine whether they return to office. Many battleground Democrats sought to keep pandemic-era migration limits in place, only to find themselves summarily ignored. And many centrists are still trying to walk a fine line on Iran, given expected deference to the Democratic president.

The Senate may take up the border security debate later this fall as part of a broad national security package, testing the potent politics of each issue. Aid for Israel is a major component of that package, potentially giving Congress a parallel opportunity to confront Iran. Republicans are already challenging Democrats on the floor.

“We want to be sure that we’re not doing anything to support Iran in this time or giving Hamas or Hezbollah any assets or any support, which we know that they’re both proxies of Iran,” said Sen. Jacky Rosen (D-Nev.), a former synagogue president who is up for reelection. “I’m confident that we’ll have a freeze on it.”

The tension between Biden’s own run and the need to keep the Senate in Democratic hands — an absolute must for governing — goes far beyond Iran and immigration. Tester, Manchin, Sinema and Sen. Angus King of Maine all voted to roll back a bank data collection rule just this week, the latest time a handful of Democrats have sided with Republican efforts to nullify Biden regulations. Manchin’s been on the warpath regarding the administration’s energy policies all year.

Critically, Democrats need to make sure their actions aren’t seen as political. Brown said that’s in part why he’s not immediately supporting bills to freeze the Iran assets: “I’m not just gonna say, out of political reasons, to do this.”

“Look at my record and why I do things and how I do things. I’ve never had a reputation of doing that,” Brown said in an interview, sticking his finger into the air for effect. As chair of the Senate Banking Committee, Brown could himself outsize sway over sanctioning Iran or other states that back terrorism.

Tester said that he would sign onto legislation freezing the Iranian assets if there is proof that Iran directed the terrorist attacks in Israel. He said that if evidence emerges that Iran is behind the killing of more than 1,500 Israelis “then I become much more frustrated” with the Biden administration’s handling of Tehran.

Save for four Democrats, including Manchin, Senate Democrats broadly supported the nuclear deal with Iran and have taken several votes over the past 10 years that Republicans may use to try to portray the party as weak on Iran. National Republican Senatorial Chair Steve Daines (R-Mont.) said any action now by Democrats is “too little, too late.”

“The American people understand that the appeasement strategy with Iran was a dangerous strategy that failed and the Biden border policy has completely failed,” Daines said. Democrats are “waking up and seeing reality,” he added.

Two Republican senators, granted anonymity to discuss internal party strategy, said they were wary of pursuing border security this fall, worried Democrats would only agree to new funding and use it for their own political and policy priorities. Sen. Joni Ernst (R-Iowa), the No. 4 leader, said Republicans need Democratic votes to beef up border security so she is “OK” with trying to work with them on it.

She also drew some nuance between the two issues, saying cracking down on Iran after the Hamas terrorist attack on Israel is “just sensible.”

“But the fact that they have pushed so hard against any sort of border security in the past, and now they’ve done this big flip-flop, it’s all political,” Ernst said.

Of course, most of the Democrats up for reelection supported the 2013 comprehensive immigration bill, which included billions for border security. The House’s snub of that bill has essentially frozen bipartisan legislative efforts on immigration now for more than a decade. Now, those moderate Democrats have little hope of expanding legal immigration along with stricter border policies.

“If we were to be able to get a comprehensive immigration bill passed with funding to secure the border, that would be a positive thing that we can hold people accountable on. Unfortunately, we don’t,” Tester said. Montanans, he added, are “concerned about folks coming across the line; we don’t know who they are. So am I, by the way.”

Beyond legislation, there’s the broader question of whether to appear with the president or not during campaign season, a question that will fall more to purple-state Democrats than those from red states. Biden is unlikely to campaign in Ohio, let alone West Virginia or Montana.

Still, some of those at-risk Democrats are welcoming Biden to their stomping grounds. The president’s almost certain to go to Pennsylvania and likely to states like Wisconsin and Nevada as well. Best not to make it awkward.

“We’re a state where results matter. And there is a proud record of accomplishment — infrastructure bill, Inflation Reduction Act,” Sen. Tammy Baldwin (D-Wis.) said. “And so I welcome President Biden to visit Wisconsin early and often.”