A recent CNN article with that headline goes into details on how Biden's team believes they can slowly chip away at the white religious voter.

The article stated:

It's a natural turn of phrase for the practicing Roman Catholic who has been waging a "battle for the soul of the nation" since he launched his 2020 presidential campaign. While the campaign's faith outreach during the primaries was narrowly focused on minority communities, Biden's team believes the former vice president could make inroads with the White Christian community, including Catholics and White evangelicals, a critical voting bloc that helped propel President Donald Trump to the White House.

"I think his own faith and values narrative allows us to have inroads into these communities in ways that Democrats might previously not have been able to do," said John McCarthy, the Biden campaign's deputy political director who works on Christian outreach.
The white evangelical vote was won by Trump last election by 81% as per CNN's article who linked to Pew Research.

The article then quotes Michael Wear who helped work on the Obama campaign back in 2012 with faith outreach. He suggested that if Biden gets 23% of this particular vote, that he could win the election.

The Biden campaign is in the early stages of developing its faith outreach efforts for the general election, including holding phone calls and small virtual events with women suburban evangelicals and millennial evangelical pastors.
Michael Wear, who directed faith outreach for President Barack Obama's 2012 reelection campaign, said he would be "shocked" if Trump loses the evangelical vote but warned of its importance: "If Joe Biden gets 23% or higher of the White evangelical vote, he wins this election."