As President Biden struggles to pull ahead in general election polling, Democratic senators are breaking away from the beleaguered candidate in early survey data ahead of the 2024 election.

A new survey from AARP found that in Pennsylvania, President Trump is leading Mr. Biden 49 percent to 45 percent in a head to head matchup, and 46 percent to 41 percent when third party candidates are included.

The same survey, however, found that Senator Casey is leading the Republican nominee, David McCormick, 48 percent to 44 percent in the state.

While polling in May of an election year is not generally predictive of an election’s final result, the discrepancy between the presidential and Senate polling is illustrative of a trend emerging in polling data in a few key states.

In Pennsylvania specifically, a recent Muhlenberg College survey found Mr. Casey leading Mr. McCormick 45 percent to 41 percent, even as Mr. Biden trails Mr. Trump 41 percent to 44 percent in a head to head.

A CBS News and YouGov survey from late April had similar results with Mr. Casey leading Mr. McCormick by 7 points even as Mr. Trump led by 1 point in the state.

A spokeswoman for Mr. McCormick, Elizabeth Gregory, tells the Sun that the campaign is content with its standing in the polls at the moment and remains confident that they’ll “retire empty suit Bob Casey and send Dave McCormick to the Senate.”

“From day one of this campaign, Dave has been laser focused on uniting the party and training our fire on career politician Bob Casey,” Ms. Gregory says.

The trend in polling, however, goes beyond just Pennsylvania. The same CBS News and YouGov poll also found that Senator Baldwin was leading the Republican nominee in Wisconsin, Eric Hovde, by 3 points even as Mr. Trump led Mr. Biden by 1 point in the presidential race.

Zooming out, this trend is playing out in swing state polling across America. In Arizona, an April Data Orbital survey found Mr. Biden leading Mr. Trump by 1 point as Congressman Ruben Gallego leads TV news host Kari Lake by 4 points in the Senate race.

In Nevada, an Emerson College and the Hill survey found Mr. Trump leading Mr. Biden by 2 points even as Senator Rosen is polling ahead of one potential GOP opponent by 14 points and another by 8 points.

In Michigan, Congresswoman Elissa Slotkin would lead any of the potential GOP nominees there, according to an Emerson College and the Hill survey even as the same pollster has Mr. Biden trailing Mr. Trump by 4 points in a one-on-one matchup.

The trend of Democratic Senate nominees breaking away from the top of the ticket could be novel to the 2024 election. In 2020, the states that voted for one party on the Senate level voted for the same party on the presidential level without exception, even in close races in Michigan, Georgia, and Arizona.

In 2022, the results of every Senate election aligned with the results of a given state’s 2020 presidential results with one exception, Wisconsin, where a republican incumbent, Senator Johnson, pulled out a 1-point victory over Lieutenant Governor Mandela Barnes.

If Democratic Senate nominees did outperform the top of the ticket it would buck a larger historic trend that Senate results have increasingly reflected a state’s presidential results.

The major recent exception to this trend came in 2018, when Democrats won Senate elections in eight states that Mr. Trump carried in 2016.

While early survey data suggests that Democratic Senate nominees may be well positioned to outrun Mr. Biden, there are a few issues to keep in mind.

First, the trend could be indicative of Mr. Biden being an unpopular nominee for his party, with FiveThirtyEight’s average of favorability surveys showing he has only about a 40 percent approval rating.

This could mean that the dynamic is less about Senate nominees outrunning the top of the ticket and more about Mr. Biden underperforming in key states.

One Republican campaign staffer also suggested to the Sun that these low polling numbers signaled that GOP Senate candidates had more room to grow and that Republicans could pick off voters who currently plan to vote for the Democratic Senate nominee but not for Mr. Biden.

More concretely, in some of these races, namely Michigan and Wisconsin, the GOP has yet to officially choose their nominee, which could throw a wrench in public opinion research.

Moreover, in each of these battleground states except Arizona it is a Democratic incumbent defending their seat against a Republican challenger.

As part of this dynamic, the incumbent typically has a name recognition advantage, especially early in the race. Incumbency also carries with it a notable fundraising and electoral advantage as well.

In 2022, for example, no incumbent from either party lost their re-election bid in a Senate race. In a typical year the vast majority — upwards of 80 percent — of incumbents will win their re-election bid.