The poll also found that 51 percent of McConnell's supporters say they "strongly" support his candidacy for re-election while 53 percent of Bevin's backers say they strongly support him.
Bevin has argued that he's a stronger candidate against likely Democratic nominee Alison Lundergan Grimes in the general election. But a matchup between Grimes and Bevin in the new NBC News-Marist poll found Grimes leading Bevin among Kentucky registered voters, 46 percent to 37 percent. By contrast, when matched against McConnell, Grimes trails the top Senate Republican 46 percent to 45 percent among registered Kentucky voters.
The NBC News-Marist poll for Kentucky was conducted between April 30 and May 6 among 2,353 registered voters. It had a margin of error of plus or minus 2.0 percentage points. Among the 408 likely Republican primary voters surveyed, the margin of error was plus or minus 4.9 percentage points.