Sen. Rand Paul (R-KY) is doing fairly well in his nascent as-yet-unannounced presidential campaign at the moment, tying for third in both Iowa and New Hampshire amidst a very crowded field; while that doesn't mean much this early on, it's not a bad place from which to start.

But the most encouraging news for his campaign this week didn't come from Iowa or New Hampshire but from his home state of Kentucky. On Saturday, the 54-member executive committee of the Kentucky GOP voted unanimously to move forward Paul's proposal to turn the state's presidential primary into a caucus, and to move it up from May to March.

That, effectively, means that Paul can run for the Republican nomination for president without giving up his Senate seat. But if he wins the presidential nomination, the problem comes up all over again.

Paul's Kentucky legal hurdle

Kentucky law specifies that "no candidate's name shall appear on any voting machine or absentee ballot more than once." Before the party moved for a caucus, the Kentucky Republican presidential primary would have been held in May, on the same day as its Senate primary. The two contests would be voted upon on the same ballot. Under that legal restriction, Paul would have had to choose whether to appear on the Kentucky ballot as a Senate candidate (in which case he'd sacrifice the chance to win delegates as part of his presidential run) or a presidential candidate (in which case he'd take himself out of the running for another term, at least as the Republican nominee).

Switching the presidential process to a caucus would remove that contest from the May ballot, enabling Paul to appear as a Senate candidate while still providing a way for him to win the state's delegates and avoid the embarrassment of losing his home state.

The plan hasn't received final approval yet. The executive committee appointed a task force to work out the rules and regulations surrounding a caucus and then present a detailed final plan for approval by the party in August. Only then is the process over. But assuming it goes through, it's smooth sailing for Paul's primary run. Kentucky Secretary of State Alison Lundergan Grimes, a Democrat who lost a Senate challenge to Majority Leader Mitch McConnell (R-KY) last year, has expressed consternation over the plan, saying it "could create potential chaos in our electoral process and severely undermine the integrity of the Commonwealth’s elections." But the parties are legally allowed to determine their presidential nomination processes, so it's unclear she could do much to undermine the plan.

The general election is still an issue

Suppose, however, that Paul beats the odds, bests Jeb Bush and Scott Walker, and emerges as the party's presidential nominee. Then the same old problem presents itself: he can be on the November ballot as a Senate candidate or a presidential candidate, but not, legally, as both. Sure, Paul Ryan and Joe Biden ran for election to the House and Senate in 2012 and 2008, respectively, while also running for vice president, but neither Wisconsin nor Delaware had this restriction.

Kentucky could theoretically change the law, and in March 2014 the Kentucky Senate passed a bill that would do just that. But the Kentucky House is controlled by Democrats, and the governor is Democrat Steve Beshear, so the proposal went nowhere. Greg Stumbo, the Democratic House Speaker, told National Journal's Shane Goldmacher, "I don't think that bill will ever see the light of day as long as I hold the gavel." Paul worked hard on behalf of Republican House candidates in 2014 but came up short, and the chamber is still in Democratic hands.

So a legislative fix is probably a no-go. But Paul could also sue to force his name on the ballot on the grounds that Kentucky's restriction is unconstitutional. In 1995, in US Term Limits v. Thornton, the Supreme Court invalidated an Arkansas law placing term limits on US House and Senate candidates on the grounds that states are not allowed to impose additional restrictions on federal officeholders beyond what's in the Constitution. Paul could argue that Kentucky's effective ban on becoming a senator if one runs for another position similarly imposes limitations not in the Constitution. Then again, lawsuits are unpredictable and time-intensive, and if Grimes is still in office, and/or Kentucky elects a Democratic attorney general this year, they could appeal all the way to the Supreme Court just to make Paul's life difficult.

Another option is to defeat Grimes in this November's election, and for her Republican successor to let Paul go forward in spite of the law. But that could prompt a legal challenge attempting to force the new secretary of state to obey the ballot law. Election-law expert Joshua Douglas, a professor at the University of Kentucky's law school, told ABC News that the "law is absolutely clear … you cannot be a candidate for more than one office in the state of Kentucky," which would put a secretary of state's decision to the contrary in legal jeopardy.

There are also more unorthodox approaches. Paul could run for either president or Senate as a write-in candidate; that may sound preposterous, but Sen. Lisa Murkowski (R-AK) won reelection in 2010 as an independent write-in contender. Paul could also designate a placeholder as the Republican Senate nominee with the understanding that he or she would resign in favor of Paul should he lose the presidential race (this only works if a Republican wins the governorship this year and can appoint Paul).

And he could always just decide not to run for reelection to the Senate if he gets the presidential nod. Sen. Marco Rubio (R-FL) has already said he'll opt out of running for Senate again if he mounts a presidential bid. But the timing could be tricky. Paul would need to be replaced on the ballot, and under Kentucky law there's no way to substitute a candidate on the ballot after the filing deadline; since the filing deadline for the Senate primary is in late January, a viable replacement would have to file by then, and then Paul would have to wrap up the nomination by May so he could drop out of the Senate race and let that replacement win the primary.

Of course, Paul could also just decide now he's running for the presidency and not the Senate — but then again, if he were willing to do that, he probably wouldn't be going to all this effort to set up a caucus.