Joe Biden was speaking in a barn to a sparse campaign crowd in Iowa when he offered a prediction. “If we defeat Donald Trump,” he said that summer day in 2019, “you’re going to see, as we say in southern Delaware, an altar call. You’re going to see people all of a sudden see the Lord.”

The Republican Party, Biden suggested, would no longer be beholden to one man. Its leaders would not be intimidated by the former president’s blowback. Politics would return to a world where the two parties could argue fiercely without vitriolic personal attacks or the embrace of falsehoods.

But on Wednesday, in the fourth month of his own presidency, Biden offered a more flummoxed, less confident assessment: “I don’t understand the Republicans.”

Biden’s political calling card for decades has been that he is one Democrat who does understand the Republicans. That ostensible familiarity caused his campaign headaches during the primary campaign; other Democrats ridiculed Republicans but Biden went out of his way to call GOP leaders “good and decent” (with Trump, he offered a qualifier: “He’s probably a decent guy.”).

Biden promoted the deals he’d cut with Senate Republican leader Mitch McConnell of Kentucky. He talked up his ability to understand the motives of the late senator Jesse Helms (R-N.C.), a figure loathed by many Democrats.

His explicit campaign message was that Trump did not represent “who we are” as a country — and the implicit corollary was that Republicans’ behavior under Trump did not reflect who they are.

“With Donald Trump out of the White House — not a joke — you will see an epiphany occur among many of my Republican friends,” he said during a May 14, 2019, trip to New Hampshire.

“If we can’t change, we’re in trouble,” he added. “This nation cannot function without generating consensus. It can’t do it.”

Biden now faces a basic question: What if he was wrong about the Republican Party? What if it has, in fact, changed in more fundamental ways than he contemplated? And if it has, what does that mean for his presidency?

Biden has watched as post-Trump Republicans, far from reverting to their previous identity, have instead embraced the ex-president with increased fervor. Republican leaders are punishing those who reject the falsehood that Trump won the election; journeying regularly to his home at Mar-a-Lago; and preparing to oust Rep. Liz Cheney (Wyo.), the third-ranking House Republican, for declining to say that Trump won.

Republicans say it is Biden who is refusing to act in a bipartisan manner, accusing him of hypocrisy after a campaign that promised conciliation. “Three months in, the actions of the president and his party are pulling us further and further apart,” Sen. Tim Scott (S.C.) said in the GOP response to Biden’s recent speech to Congress.

As the disconnect has persisted, Biden’s predictions have grown more dire.

“I have no idea if there will be a Republican Party. Do you?” Biden responded a few weeks ago when asked whether, if he ran in 2024, it would be against Trump.

His rhetoric now has almost a “bless their hearts” tone, professing to speak more in sorrow than anger. He claims to not quite understand a party that restricts voting or challenges science, one that won’t rid itself of Trump or stand by Cheney. (Biden once called Cheney’s father, Richard B. Cheney, who preceded him as vice president, “a decent man,” earning the wrath of fellow Democrats.)

The president said this week that while his own party has engaged in plenty of internal fights, it doesn’t compare to the Republican warfare: “I don’t ever remember any like this.”

The current GOP is certainly not the party that Biden used to know, the party of Ronald Reagan, of George H.W. Bush or George W. Bush. It’s not the party that nominated John McCain and Mitt Romney for president.

Biden’s history of predicting that Republicans will come around — after the next election, the next soul-searching, the next reality check — is a long one.

“I think you’re going to see the fever break,” he predicted on MSNBC on Nov. 4, 2012, shortly before then-President Barack Obama’s reelection.

“There’s a dozen Republican senators, and I think I can name you two-and-a-half, three dozen Republican House members who, once this election is over, they kind of get a get-out-of-jail free card,” Biden added. “They’re going to start saying, ‘Hey, man, I no longer have an obligation to stick with the right of my party.’ ”

That, most would agree, did not happen.

Two years later, in 2014, Biden predicted that Democrats would keep the Senate majority (which they did not) and things would change. “What’s going to happen is, it’s going to break the back of the hard right and you’re going to see reasonable people in the Republican Party start to vote reasonably again,” he forecast.

That shift, too, didn’t happen.

And the current lack of a Republican epiphany?

“Well, I’ve only been here six weeks, pal, okay? Give me a break,” Biden said with a laugh when asked about it last month by ABC’s George Stephanopoulos. Biden then amended his prediction, saying the epiphany would occur sometime “between now and 2022.”

Biden’s optimism is all the more striking since Republicans have rarely given him an opening, perhaps most especially not now.

“One-hundred percent of our focus is on stopping this new administration,” McConnell said on Wednesday, adding that Biden and the Democrats want “to turn America into a socialist country, and that’s 100 percent of my focus.”

That was reminiscent of McConnell’s comment in 2010 that “the single most important thing we want to achieve is for President Obama to be a one-term president.”

Such statements have not deterred Biden.

“Look, he said that in our last administration with Barack — he was going to stop everything,” Biden said on Wednesday. “And I was able to get a lot done with him.”

What Biden left unmentioned was how many things McConnell helped block, including gun control in 2013 and a Supreme Court nomination in 2016.

But a new tone of doubt has crept into Biden’s assertions about the Republicans’ path.

“It seems as though the Republican Party is trying to identify what it stands for,” he said on Wednesday. “And they’re in the midst of a significant, sort of, mini-revolution going on in the Republican Party.”

He added: “We badly need a Republican Party. We need a two-party system. It’s not healthy to have a one-party system. And I think the Republicans are further away from trying to figure out who they are and what they stand for than I thought they would be at this point.”