DETROIT — When President Joe Biden held a rally here last week and soaked up the adoration of supporters, scores of prominent Michigan Democrats joined him — with one notable exception: Rep. Elissa Slotkin, the party’s top candidate in a must-win Senate race.

The rally came in the midst of a divisive intraparty spat about whether Biden should remain the Democratic nominee or step aside after a bewildering debate performance and polls saying he’s narrowly trailing Donald Trump nationally and in key states. Slotkin has said only that it’s Biden’s decision to make; her campaign said she had a scheduling conflict and couldn’t attend.

“We’ve been saying since day one this would be one of the closest Senate races in the country,” Slotkin campaign spokesperson Antoine Givens said. “That’s why we’ve been building a grassroots campaign prepared to make the contrast clear between Elissa’s record of delivering for middle-class Michiganders and any of her Republican opponents.”

Slotkin’s absence from the Biden rally comes amid an unease among down-ballot Democrats who party strategists believe will outrun Biden, yet worry that he could drag them down. But ticket-splitters — those who vote for a different party for president than for down-ballot candidates — are a shrinking breed. In dozens of contested Senate races during the last two presidential elections, only one state delivered a split result: Maine in 2020 voted for Biden and centrist GOP Sen. Susan Collins. Not a single state split the vote in 2016.

“There are definitely ticket-splitters,” said Abby Clark, a Democratic organizer and former campaign aide in Detroit, who is calling on Biden to exit the race. “But overall those tides rise and fall together. Michigan is always very tight. A real collapse in support for the top of the ticket will have a huge impact on all the other races.”

“Even with Slotkin running ahead of the president — how much ahead is possible?” Clark said. “There’s intense fear about the situation we’re in and what it means.”

Democratic candidates are outpolling Biden

Polls taken before and after the June 27 debate paint a consistent picture: Democratic Senate candidates in key states are faring well and broadly leading GOP rivals, while Biden is in a dead heat with Trump or trailing him with the same set of voters. In some more recent polls, Biden has been underperforming other Democrats by 5 points to double digits.

In Michigan, a recent EPIC-MRA poll found Biden trailing Trump by 3 points, while Slotkin led Republican Senate front-runner and former congressman Mike Rogers by 2 points — both within the margin of error.

While Slotkin keeps some distance from Biden, Rogers has embraced his party’s nominee, vowing at the Republican convention this week to “fight alongside Donald Trump” if elected. Rogers spokesman Chris Gustafson linked Slotkin to Biden, saying: “With all of the problems Joe Biden has caused for hard-working Michigan families, his debate performance should be the least embarrassing thing about Elissa Slotkin still supporting him.”

Biden has dismissed fears that he could harm the ticket, pointing to the Democrats’ overperformance in the 2022 midterms and special elections since he took office. His campaign predicted the party will win up and down the ballot.

“Led by Joe Biden, Democrats have an incredible agenda to run on. Republicans every single day of this cycle are forced to answer for their support for abortion bans, shipping jobs abroad, and undermining our democracy,” Biden campaign spokesperson Mia Ehrenberg told NBC News. “This election, whether it’s top of ticket or a state election, will be decided on the issues that matter most to voters, which is why Democrats will win this November.”

Still, Democrats like Slotkin cannot afford to fully abandon Biden for risk of upsetting the scores of base voters who still passionately support him and demand that members of his party do the same. At Biden’s rally in Detroit, some voters praised Slotkin and said she should have the space to run her race, but others said they wouldn’t look kindly upon candidates who are disloyal to the president.

Deanna Zapico, a Biden supporter who came to the rally Friday from Royal Oak, Michigan, praised Slotkin.

“Love her. She’s a really strong candidate,” Zapico said, adding that she trusts Slotkin’s judgment on not campaigning with Biden. “If she needs to do that, then she needs to do that. That’s fine. It might help her if she were here.”

But Lakshmi Vadlamudi, a rally attendee from Franklin, Michigan, said she’s “extremely angry” at those Democrats calling on Biden to withdraw from the race.

Slotkin has not issued such a call, telling The Detroit News that she’s soliciting voter input on the question.

Asked about Slotkin skipping the Detroit rally, Vadlamudi said she’s “going to be skeptical of anyone” in down-ballot races who doesn’t stand by the president, saying such calls only weaken the party.

‘A dramatic drop in Biden’s numbers’ from 2020

In Pennsylvania, a New York Times/Siena poll found Biden trailing Trump by 3 points (inside the margin of error), while Democratic Sen. Bob Casey led GOP rival David McCormick by 8 points among likely voters (outside the margin).

Asked why he believes he’s outperforming Biden in Pennsylvania polls, Casey told NBC News, “It’s really early so people haven’t focused.”

He added that he prefers “not to analyze” the polling and just make his case as a candidate. “We’re in a tough race,” Casey said.

In Wisconsin, a bipartisan Fabrizio/Impact poll found Biden trailing Trump by 6 points, while Democratic Sen. Tammy Baldwin led GOP rival Eric Hovde by 5 points, both within the margin of error.

In an even more stark example, a Times/Siena poll of Democratic-leaning Virginia found that Biden leads Trump by just 3 points (inside the margin of error), while Democratic Sen. Tim Kaine led GOP opponent Hung Cao by 17 points.

That leaves a few possible scenarios in the three-and-a-half months until Election Day. One is that “double haters” of both presidential candidates return to Biden and his numbers rise closer to the other Democratic candidates. Another is that Biden is an anvil dragging down-ballot Democrats down. And a third is that the picture largely holds and 2024 produces the most widespread ticket-splitting in over a decade.

Jessica Taylor, who oversees Senate races for the nonpartisan forecaster Cook Political Report, said the disparity is due to Biden’s slipping support. Cook recently shifted the rating of the Michigan Senate race from “lean Democrat” to “toss-up.”

“We haven’t seen Trump’s numbers change a lot since 2020. What we have seen is a dramatic drop in Biden’s numbers,” Taylor said. “Look at the debate and the freezing — I fully understand why Senate Democratic candidates don’t want to be there with Biden.”