Sen. Rand Paul (R-Ky.) is seeking to run for two offices at the same time. (J. Scott Applewhite/AP)

Sen. Rand Paul (R-Ky.) got a major ally Tuesday in his endeavor to run for both president and the U.S. Senate at the same time: Senate Majority Leader Mitch McConnell.

Paul has asked the Kentucky Republican Party to hold a presidential caucus in 2016, rather than have residents choose their presidential nominee in the state's primary.

Why? Kentucky law prohibits a candidate from appearing on the ballot for two offices. Paul announced late last year that he's running to keep his Senate seat and said this week that he is leaning toward a presidential run. A caucus doesn't have ballots, and the proposed contest would choose only the presidential nominee; voters would choose nominees for other offices, including the Senate, during the May primary.

McConnell was suspicious of the plan. But after a conversation with Paul, he threw his support behind the idea.

"Senator McConnell's initial reaction to the caucus proposal could best be described as respectful skepticism," McConnell's chief of staff, Brian McGuire, said in a statement. "But after a lengthy discussion of the details with Senator Paul he has become convinced that switching from a primary to a caucus is worth his support. Not only would it be helpful to the Senator's presidential campaign but, as a one-time event paid for with funds that he'd raise, would do no damage to the state party or interfere with this year's state races." 

Paul has asked the state party to vote on the proposal during a March 7 meeting in Bowling Green.

"Senators Paul and McConnell agree that holding a presidential caucus in 2016 is both doable and a good idea – for Senator Paul, the Republican Party and Kentucky, which will have a bigger voice in the presidential selection process. We look forward to presenting their support to RPK and its committees and moving forward united as a Party," Doug Stafford, a senior adviser to Paul, said in a statement.

Kentucky Secretary of State Alison Lundergan Grimes, who lost to McConnell in November by 15 points, has threatened to take Paul to court to prevent him from running for both offices at the same time.

According to the Lexington-Herald Leader, Paul's supporters believe the law is unconstitutional. The paper also reported that Paul wrote in a letter to state Republicans that "moving up Kentucky's presidential primary election would also allow me to make a run for the nomination and seek re-election." He also pointed to a candidate who ran for two offices simultaneously: former vice presidential nominee and current Rep. Paul Ryan (R-Wis.).