The poll, conducted by Democratic firm Public Policy Polling, shows him leading both Kentucky Secretary of State Alison Lundergan Grimes and former Rep. Ben Chandler (D-Ky.) by only single-digit margins and failing to crack 50 percent against both.
McConnell also faces a tough climate for reelection, with a majority, 54 percent of respondents, saying they disapprove of his job performance, while 36 percent approve.
Among Republicans, however, a slight majority, 53 percent, approve of his performance, while 34 disapprove. That he still gains majority support from Republicans indicates a primary challenger may have a tough time defeating him — and, indeed, one has yet to emerge.
Against Lundergan Grimes, McConnell takes 45 percent support to Lundergan Grimes's 41 percent. Against Chandler, he has a similar lead, with 46 percent support to Chandler's 41 percent.
But those numbers come before either of those Democrats have entered the race, and before McConnell's campaign has begun its offense against them. And the poll indicates there's room for McConnell to define either Lundergan Grimes or Chandler before the race picks up.
Though Lundergan Grimes is the only potential contender of all three to have her favorability above water, with 28 percent of respondents saying they view her favorably, while 22 percent have an unfavorable opinion, a full 50 percent of respondents say they're unsure of how they feel about Lundergan Grimes.
Though the secretary of State is considered by Kentucky Democrats to be a strong contender, she'd clearly have to launch a campaign soon if she hopes to raise her profile in the state, and get out ahead of McConnell on messaging.
Chandler is seen less favorably than Lundergan Grimes, likely because he's had a longer tenure in Kentucky politics than her. Thirty-four percent of respondents have an unfavorable opinion of him, while 25 percent have a favorable opinion. Forty-one percent of respondents are unsure how they feel about him.
National Republican Senatorial Committee spokesman Brad Dayspring dismissed the poll, saying that the lack of a Democratic challenger indicates McConnell is actually in a strong position for reelection.
"Kentucky Democrats obviously see a different reality than PPP, which is why the only running they are doing is away from this Senate race. Neither Watergate-style tactics nor Hokus Pokus [sic] numbers from PPP are going to change the reality in Kentucky, no matter how much Washington Democrats may click their heels and wish it so," he said.
On Tuesday, tapes of a private meeting between McConnell and his campaign team were leaked, in which he and his advisers can be heard discussing potential lines of attack against Judd and Lundergan Grimes. McConnell's campaign is working with the FBI to investigate the tapes, which they say were recorded without consent.
Without a candidate, Democrats haven't had as much of an opportunity to go on offense over the past few months, and McConnell's approval, though low, has stayed steady since PPP's last poll, in December.
Actress Ashley Judd, however, does seem to have suffered since she first indicated her interest in a Kentucky Senate campaign. She decided last month against running, but it looks like, had she chosen to run, she would've had to do some damage control — her approval is now underwater, with 34 percent viewing her favorably and 41 percent viewing her unfavorably.
Her shift in numbers, from 42 percent of respondents viewing her favorably in December, indicates attacks by outside groups and Democrats critical of her potential candidacy took a toll on her public image.
The PPP poll was conducted among 1,052 Kentucky voters, including 320 likely Republican primary voters, from April 5-7 and has an overall margin of error of plus or minus 3 percentage points and plus or minus 5.5 percentage point for the Republican portion.