“He’s not like his father,” said one Republican ally of Paul’s, referring to former Texas Rep. Ron Paul’s refusal to quit in 2012 despite the steep odds.

The presidential campaign is marking a new chapter in the McConnell-Paul political alliance that began immediately after Paul upset McConnell’s handpicked candidate in the GOP primary. Since then, McConnell has moved aggressively to take Paul under his wing. McConnell relied on the libertarian-leaning senator’s popularity and appeal to the conservative grass roots as the two barnstormed Kentucky during the GOP leader’s successful reelection bid last year. Now, Paul is calling in the favors.

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“We’ve worked together on so many things that I just thought it was a furtherance of our friendship and alliance, and sort of a logical conclusion,” Paul said of winning McConnell’s endorsement to change the presidential primary to a caucus.

Still, while McConnell publicly backs Paul’s presidential run, it’s doubtful the GOP leader will do much fundraising for his colleague’s White House hopes.

“Sen. McConnell has made his support for Sen. Paul clear, but he also has a job to do,” said Brian McGuire, McConnell’s chief of staff. “He has no plans at this time to do any presidential campaigning.”

Paul’s maneuvering intensified immediately after McConnell’s reelection. At McConnell’s election night party in Louisville, Paul buttonholed the state party chairman, Steve Robertson, and the two had a half-hour discussion about the far-reaching idea to turn the presidential primary into a caucus system. That presumably would circumvent the prohibition of appearing on the ballot twice in the primary since a caucus would not rely on a paper ballot.

Earlier this month, the state party’s 50-member executive committee endorsed Paul’s caucus proposal, despite concerns from some committee members over the cost of the proposal and whether it would disenfranchise absentee voters. A proposal that includes all the logistics of holding a caucus over a primary and addresses those concerns will be presented to the 350-member full committee, which rarely bucks the executive committee, in August. Proponents say moving up a caucus to March in the presidential calendar would give the Bluegrass State a bigger say in the nominating process than if the primary remained in May.

“This is the first time we have taken up an issue of this magnitude,” Robertson said. “It’s a proposal that’s going to have to be well constructed. … We are just beginning the work of putting the details together.”

Paul’s eligibility hinges on a Kentucky election law that stipulates: “No candidate’s name shall appear on any voting machine or absentee ballot more than once,” other than in certain special election situations. The law allows the state party to replace a candidate on the ballot in case of death, disqualification or “severe disabling condition which arose after the nomination” as long as it’s before the mid-September deadline to certify candidates.

If Paul ends up winning the GOP’s presidential nomination, party officials could go down the complicated path of suing to keep his name on the ballot for the Senate race or trying to replace him with a different candidate. A new candidate would have only a few months to campaign, however. A placeholder candidate, who would have to file for office by January’s deadline and compete only if Paul were to stay in the presidential race, would add its own political and legal complications.

And if Paul were to resign and let a new senator take his place, the governor — who will be elected this year — would appoint the new senator. (Polls show a close race between likely Democratic nominee Jack Conway, who was defeated by Paul in the 2010 Senate race, and three Republicans vying for the party’s nomination.)

“I think it does add an element of interest certainly to the governor’s race,” said Eric Lycan, who served as counsel to McConnell’s 2014 campaign.

If Paul is on the ballot, it will be much harder for Democrats to win in the conservative state. But all bets are off if it suddenly becomes an open seat — or if the GOP incurs a loss in court.

“Absolutely, we can compete in Kentucky,” said Montana Sen. Jon Tester, head of the Democratic Senatorial Campaign Committee. “They’ve got 24 seats up; there are a dozen of them we can compete in, and Kentucky is one of them.”

Even after the Kentucky GOP officially endorses the caucus proposal, the path forward remains uncertain and will likely be full of hurdles for Paul. Democrats are likely to do more than challenge the ballot issue in a general election — they’re also expected to file a lawsuit over the caucus system, arguing it disenfranchises voters.

“At the end of the day, this is all going to court. Nothing is going to happen until next January after the filing deadline,” said Scott White, an election lawyer who worked for Alison Lundergan Grimes, the Democratic candidate whom McConnell vanquished last year. “Sen. Paul has come up with a scheme — and you gotta give him credit, it’s clever. But at the end of the day, it’s the height of selfishness.”