A campaign without Biden? Republicans offer a glimpse of how that might look

Here's a sneak peek into a campaign that still doesn't exist. A glimpse at a U.S. presidential election without Joe Biden. There are early signs of itin Milwaukee.

At their national convention, Republicans are already testing new lines of attack against the likeliest replacement if Biden drops out: Vice-President Kamala Harris.

The party is performinga half-pivot in the midst of its convention, which is unfolding amida fog of uncertaintyas Biden's allies rampup pressure to push him out.

Republicans are previewing the hard hits theyintendto toss Harris's way if she replaces Biden atop the Democratic ticket, with a top Trump official publicly testing somemessages.

Republicans test 'coup' message

Message No. 1: that forcing out the nominee after the primaries is an anti-democratic act, and Republicans made clear they'll throw it back atDemocrats whenever they mention Jan. 6 and Trump's threat to democracy.

"It's literally a coup," said Donald Trump's co-campaign manager Chris LaCivita, speaking Thursday at the convention, at a panel hosted by news outlets Politico and CNN.

WATCH | 3ways Democrats could replace Biden:

3 ways the Democrats could replace Joe Biden | About That

3 months ago

Duration 11:43

As a growing number of Democrats call for Joe Biden to drop out of the 2024 U.S. presidential race ahead of the Democratic National Convention, About That producer Lauren Bird breaks down the options to replace him on the ballot and what makes some of them especially challenging.

"This is nothing more than an attempted coup by the Democratic Party," he said. "They're going to disenfranchise millions of people who [voted in primaries for Biden]."

Message No. 2: that Harris owns every failure of the Biden administration, especially the porous border, which was supposedly her file. "The border czar," LaCivita said, mockingly. "Last time I checked it's Biden-Harris."

Message No. 3: that Harris lied to the American public by insisting Biden was mentally up to the job, before replacing him. "Gaslighter-in-chief," LaCivita said, promising attack ads on Harris vouching for Biden: "Do you know how much tape we have on this?"

The campaign boss all butadmitted Trump's team has startedspending resources on a changed campaign.When asked whether he's begun doing polls on Trump versus Harris, he replied:"What the hell do you think?"

The Harris factor has been palpable all week in Milwaukee where her name has come up dozens of times in speeches. This is sure to escalate now, with reports that the biggest namesin the Democratic Party are pressing for a change atop the ticket.

This includes Senate leader Chuck Schumer personally driving to Biden's home in Delaware to reportedly ask him to leave; a reportedly similar message conveyed to Biden by House leader Hakeem Jeffries, a public call for Biden to step aside by Congressman Adam Schiff, a top ally of Nancy Pelosi, and the deepest cut of all for Biden: Barack Obama reportedly telling allies his formervice-president should reassess his run.

Notably,none of these party figures are denying those reports.

New candidatewould give Dems 'energy'

One prominent Republican is warning his party to prepare for a tougher race. New Hampshire Gov. Chris Sununu said the pressure for Biden to leave will only escalate after the Republican convention ends Thursday.

"It's real, it's happening," Sununu said at the same Politico/CNN event, although he appeared via video.

He predicted that replacing Biden would not simply energize the Democratic Party; he said it would also win back some swing voters who dislike the elderly candidates currently on offer, Trump and Biden.

"That is a very different race than running against Biden," Sununu said.

WATCH | Democrats divided on Biden staying in the race:

Democrats divided over Bidens future

3 months ago

Duration 2:39

Members of the Democratic Party remain divided over whether Joe Biden should drop out of the U.S. presidential race or if the party needs to come together and fight a common enemy Donald Trump.

"Believe me: if and when they make the switch, everything's going to change. It's going to get very close in a lot of those tighter states. There's going to be more energy. The Democrat Party will be rewarded, if you will, by independents saying, 'None of us liked that whole Biden-Trump ticket to start with you guys had the courage to change your nominee.' "

That political read comes from a unique place: Sununu is a Republicanwho has, on the one hand, recently endorsed Trump,but,on the other, repeatedly criticized his party's nominee more aggressively than most Republicans.

Republicans revel in Democrats' turmoil

The Democrats' turmoil has been a frequent topic of conversation at an unusually buoyant Republican convention.With favourable polls and their rivals split and bickering, Republicans are in a jubilant mood this week.

One convention-goer said it doesn't matter who the Democrats nominate.

"I think [Harris would] get crushed," said Andrea Fletcher, a convention attendee from Wheaton, Illinois.

"I think she is more unliked than Biden."

As for the prospect of the president bailing on his own re-election bid, Fletchedadded: "I'm not surprised at all at this point. It seemed like the writing was on the wall for a while."