Replacing Biden on ticket would be 'unlawful' in some states, Johnson claims. Experts disagree.

Just hours before President Joe Biden announced he was stepping down from the 2024 race, House Speaker Mike Johnson said Sunday that such a move might lead to legal challenges.

Johnson, R-La., told ABC "This Week" co-anchor Martha Raddatz that it would not be possible for some states to switch out Biden for another candidate ahead of the presidential election in November.

"So, it would be wrong, and I think unlawful, in accordance to some of these states' rules for a handful of people to go in a back room and switch it out because they're, they don't like the candidate any longer. That's not how this is supposed to work. So I think they would run into some legal impediments in at least a few of these jurisdictions," he told Raddatz.

"I think there'll be a compelling case to be made that that shouldn't happen, and so I think they've got legal trouble. If that's their intention, and that's their plan. So we'll see how it plays out," he continued.

Election law expert Richard Hasen wrote that there is "no credence" to the notion that the Democratic Party could not legally replace Biden on the ticket, as he is not the nominee yet -- the nominating process generally takes place during the Democratic National Convention.

"Joe Biden is not the party's nominee now, and states generally point to the major party's nominee as the one whose name is on the ballot," he wrote in a piece earlier this month.

Raddatz asked Johnson on Sunday about how Republicans might approach the race differently if Vice President Kamala Harris were to replace Biden as the Democratic nominee.

"It doesn't matter who they put at the top of the ticket," Johnson said. "If Kamala is the nominee, so be it. She is the co-author and the co-owner of the policies of the Biden administration, and she owns all these policy failures herself."

In an ABC News/Washington Post/Ipsos poll published last week, Harris led Trump 49-46% among all adults if she replaced Biden as the Democratic nominee.

"I mean, it's no contest, and everybody knows that, and I think that's why we're in such a good position. I think this election should not be about personalities, but about policies," Johnson said.

Raddatz pushed back, noting that former President Donald Trump called Harris "crazy" and "nuts" at a rally in Grand Rapids, Michigan, on Saturday night.

"President Trump was attacking her personally, as you know, last night," Raddatz said. "He wasn't really talking about her policies."

Johnson responded that Democrats have lobbed the same kinds of verbal jabs against Trump.

"We could run the tape of the terrible things that Kamala Harris has said about Donald Trump, of course, and Biden, as well, and everybody in the Democrat leadership. I mean, we're accustomed to it now. It's their standard practice," Johnson said.