Now Trump wants Biden? Republicans threaten to sue to keep Harris off ballot.

A whole new election for president launched Sunday, and America's two major political parties immediately zeroed in on fresh priorities.

The Democrats are prepping what will appear to be a cordial and collegial contest for the party's nomination before officially declaring Vice President Kamala Harris as President Joe Biden's replacement at their convention in Chicago next month.

The Republicans are threatening to rush to courts to ask judges, in what would be predictably anti-democratic filings, to prevent voters from supporting any candidate for president not named Donald Trump in November.

The order of things has been unprecedentedly upended with Biden's announcement Sunday that he would no longer seek his party's nomination.

The Democratic Party's spasms of angst about the 81-year-old president's ability to handle the rigor of campaigning have been swiftly replaced with an enthusiastic kumbaya for the 59-year-old Harris at the top of the ticket. The Republican Party, which has been hammering Biden about his age for months, now has a 78-year-old former president as its nominee.

Kamala Harris seems to have clear path to Democratic nomination

For Elaine Kamarck, a senior fellow at the Brookings Institute and a member of the Democratic National Committee's rules committee since 1997, this new campaign is both extraordinary and, now, predictable.

The party's convention rules committee will meet virtually on Wednesday and draft a report on how to run the show in Chicago. Kamarck told me she expects that report to be adopted when the Democratic National Convention opens on Aug. 19.

Kamarck also expects the DNC to stick to a previous plan to hold a virtual meeting sometime between Aug. 1 and the convention to vote on a nomination for president. The rules remain the same for any Democrat trying to take on Harris – they would need a nomination petition signed by at least 300 of the nearly 4,000 party delegates to get a roll call vote.

A USA TODAY count of delegates shows that Harris is nearly halfway to the 1,968 delegates needed to become the party's nominee in the first round of voting.

Gen Z wanted Biden gone. Now we have to prove Kamala Harris is the best way to beat Trump.

Kamarck doesn't expect a serious challenger to emerge for Harris. The money bomb that went off after Biden endorsed Harris on Sunday, $81 million in campaign donations in the 24 hours after she announced her bid for the top of the ticket, shows a unifying surge in momentum for her.

Harris, now in the process of picking a vice presidential running mate, appears to have this all sewn up.

Republicans seem ready to challenge Harris' taking over

The Republicans, by contrast, are scrambling to redirect rhetorical attacks at Harris and threatening to file toothless lawsuits not meant to be taken seriously by courts but instead meant as messaging for an aggrieved base of voters always willing to see fair play as foul behavior.

House Speaker Mike Johnson, who would never let principles impede his partisan politics, told ABC News on Sunday that it would be somehow "unlawful" and a source of "legal trouble" for the Democrats to swap candidates on and off the ticket. Johnson, a lawyer, offered no legal rationale for this. That's because he doesn't have one.

This is, of course, the same Mike Johnson who railed against attempts by some states earlier this year to keep Trump off the ballot by employing a post-Civil War constitutional provision barring insurrectionists for office. In March, the Supreme Court rejected the state attempts.

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After the ruling, Johnson denounced the effort as "a purely partisan attack," accused the states of "undemocratic behaviors" and said they should "leave it to the American people to decide who will be president."

The speaker's raging case of hypocrisy can't come as a surprise. He was all in on election denialism in 2020 and the attempt to disenfranchise millions of voters – Democrats, Republicans, independents and others – because Trump couldn't accept that he had lost. The many Republican legal maneuvers all crashed and burned in courts.

Can Harris take the White House, given the late start?

Allan Lichtman, a history professor at American University renowned for correctly predicting the results in the last nine out of 10 presidential contests, is waiting until after the Democratic convention to make a call this year.

While he previously suggested that the party should stick with Biden, he saw upsides for Harris now that she appears headed to the nomination.

"She can certainly win in an open seat so long as you have the united party," Lichtman told me. "I think the Democrats have learned their lesson about engaging in self-destructive attacks out in public. I think they're going to, at all costs, avoid that."

Republicans have nothing to fear: Biden is out, but Trump, GOP won't have to change their message. Harris isn't much better.

As for the Republican threats of legal challenges, Lichtman was unimpressed.

"That's just a lot of propaganda by Republicans to try to throw a monkey wrench in this," he said. "I think it has zero chance of succeeding."

2024 presidential election took a sharp turn, but we're getting clarity

The general election is 15 weeks away. The only certainty for now is uncertainty. We've jumped from the historic – a former president trying to defeat the president who beat him – to the unprecedented – a vice president stepping up to the top of the ticket this late in the game.

Trump sounds nervous, taking to his social media site Monday afternoon to call Harris "Dumb as a Rock."

He had previously agreed to a Sept. 10 debate with Biden hosted by ABC News but now is huffing and puffing about how unfair it might be. That sounds like the opening gambit to avoid sharing a stage with Harris.

The vice president, by contrast, sounds confident. She is enjoying a flood of support, in endorsements and donations, in just two days. We'll see whether this newfound Democratic resolve can last the distance.

Follow USA TODAY elections columnist Chris Brennan on X, formerly known as Twitter: @ByChrisBrennan

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This article originally appeared on USA TODAY: Hypocritical GOP threatens lawsuits to keep Harris off the ballot