Sen. John McCain, taking a victory lap as the presumptive Republican nominee, happily poked fun at his only remaining opponent.
Asked during an appearance on "The Daily Show" last week which of the two Democratic nominees he preferred to run against in the general election, McCain quipped, "Ron Paul."
But Paul might get the last laugh during McCain's coronation at the party's convention in early September.
McCain's nomination may be certain, but he finds himself pressured by different wings of the conservative movement -- from the libertarians and the anti-war activists, to social conservatives and evangelical voters.
In recent primaries, as many as 25 percent of Republican voters chose a different candidate, with many pulling levers for Paul and former GOP candidate Mike Huckabee, who snagged 27 percent of the vote in the Pennsylvania primary.
A similar phenomenon also occurred in 2000, when 33 percent of Republicans voted against Bush in the Colorado primary though Bush was the presumed nominee by then.
Paul's grass-roots movement of enthusiastic supporters is reportedly planning a minirebellion at the convention to push its anti-war, anti-tax agenda.
In state conventions in Maine and Nevada, Paul's forces battled McCain's delegates to the brink. While they won't have the muscle to challenged McCain in the national convention, they can be an annoying sideshow when the spotlight is supposed to be solely on the candidate.
Huckabee has endorsed McCain, but some of his evangelical supporters remain skeptical about McCain's claim to be a social conservative.
Virginia conservative Michael Farris, the chancellor of Patrick Henry College, reportedly promoted an Obama presidency as a biblical punishment for Republican sins, which would allow the party to regroup and come back under the leadership of Huckabee in 2012. Farris denied that he ever suggested such a thing during an interview with ABCNEWS.com.
And former GOP Rep. Bob Barr, who won acclaim in conservative circles for leading the drive to impeach President Clinton, just announced his run for the presidency on the Libertarian Party ticket.
The party commands few votes, but Barr has the potential to draw away Republican voters and be a spoiler in battleground states as Ralph Nader was accused of doing to Democrats in the 2000 election.
Though McCain's nomination at the convention is assured, it may not be a love fest and that concerns Republicans who are warily eying a resurgent Democratic Party that has galvanized millions of new voters.
"What's happening with Ron Paul cannot be ignored by John McCain," said Greg Mueller, a Republican consultant not affiliated with any campaign.
"You need every vote, whether it's a social conservative, a tax conservative or a national defense conservative. Like the social conservatives, if that vote had been ignored, George Bush would not have made it in 2000. … They have to be excited, energized to get other people to vote."
A spokesman for the McCain campaign emailed: "We're very pleased by the overwhelming support that John McCain is receiving from all levels of the Republican Party, something that has not been seen after other open primaries in the recent past, and are now mobilizing them towards the convention and the get out the vote operation in the general election in November."