WATERTOWN, Wis. — A new Marquette Law School poll conducted before Tuesday’s contentious debate has Vice President Kamala Harris opening up a 4-point advantage in the battleground state of Wisconsin.

And voters’ religious affiliations are a big reason, with a dramatic split emerging between Christians backing former President Donald Trump and atheists, agnostics and those from other faith traditions siding with Harris.

The poll’s two-way ballot test shows a whopping 82% of likely voters who say they have “no religion” support Harris, compared with 17% behind Trump.

Among respondents who identify as something other than Protestant or Catholic, 55% back the vice president, while 30% support the former president.

The numbers flip when it comes to those who embrace Christianity: 75% of born-again Christians support Trump in the binary battle, while 54% of Catholics say the same thing.

Mainline protestants are split; both Trump and Harris are at 46% among that group.

Church attendance is also a strong indicator of support for Trump, with 63% of those who show up more than once a week backing him, along with 55% of weekly attendees and 67% of those who attend up to twice a month.

Among those who never go to church, 72% back the Democratic nominee.

The religious data underscore a race marginally tipping Harris’ way, at least according to this survey.

In July, the polling group had Harris and Trump essentially tied. Now Harris is the choice of 52% compared with 48% for Trump for both likely and registered voters.

Robert F. Kennedy Jr. — who has filed yet another legal challenge in an attempt to remove his name from the Wisconsin ballot — garners a neat 6% of the vote among registered voters when all candidates are added to the polling, bumping Harris down to 47% and Trump down to 43%.

Regardless of religion, Democrats are more likely to say they’re “very enthusiastic,” with 72% making that claim compared with 63% of Republicans.

If Trump wants to make inroads in the Dairy State, economic messaging may be the key.

Independent voters put the economy at the top of most important issues this election, followed by Medicare and Social Security. For Republicans, the economy and immigration are still the most important determinants of their vote, while other issues rank much lower.

Overall, 41% of voters surveyed ranked the economy as the most important, 15% put abortion at the top, and 12% said immigration and border security.

Democrats named abortion policy their number-one issue, with the economy 1 percentage point behind.

Both candidates are underwater in terms of favorability. Harris is at 47% approval and 51% disapproval; Trump is worse off, with 43% approval against 56% disapproval.

The Marquette Law School poll surveyed 738 likely voters from Aug. 28 to Sept. 5, with a +/-4.7 margin of error. This means that despite the Harris edge, Trump is still in the game.