Sen. Rand PaulRandal (Rand) Howard PaulNSA spying program overcomes key Senate hurdle Fix what we’ve got and make Medicare right this year Despite amnesty, DACA bill favors American wage-earners MORE (R-Ky.) on Thursday warned that Senate Majority Leader Mitch McConnellAddison (Mitch) Mitchell McConnellSessions: 'We should be like Canada' in how we take in immigrants NSA spying program overcomes key Senate hurdle Overnight Finance: Lawmakers see shutdown odds rising | Trump calls for looser rules for bank loans | Consumer bureau moves to revise payday lending rule | Trump warns China on trade deficit MORE (R-Ky.) faces a tough reelection fight.

"My guess would be that the general election is fairly close," Paul told The Herald-Leader of McConnell's prospects.

Paul, who has endorsed the GOP leader for reelection, said he he believes McConnell will defeat primary challenger Matt Bevin, saying he doesn't believe the primary is "particularly close at this point."

McConnell is viewed with suspicion by many conservatives who have balked at some of the deals he has negotiated with Democrats.

Paul complimented Bevin as a "good, honest, Christian man" on the day he filed his candidacy, prompting some to wonder about Paul's commitment to McConnell.

Assuming he wins the primary, McConnell is expected to face Kentucky Secretary of State Alison Lundergan Grimes in the general election. Grimes is a highly-touted recruit who's expected to raise substantial sums and, as a young female candidate she could create a strong contrast with McConnell.

Multiple polls have shown her running even or slightly leading the Senate minority leader, who remains unpopular in his home state. Democrats are looking to Kentucky as their top pickup opportunity this cycle.