Maryland Gov. Martin O’Malley (D) threw his weight behind state Sen. Robert Garagiola (Montgomery) Thursday, even as John Delaney’s campaign released an internal poll showing the financier with a wide lead in their contest for the Democratic nomination in the state’s lone competitive congressional race.

Delaney, Garagiola and Air Force doctor Milad Pooran are the highest-profile Democratic candidates in the redrawn seat currently held by Rep. Roscoe Bartlett (R). Delaney and Garagiola have each attracted some high-profile backers in the race, and O’Malley has now added his name to the other major Democrats endorsing Garagiola.

Before Thursday’s endorsement, O’Malley praised Garagiola Wednesday night in an interview with The Post.

“If I lived in the 6th [congressional district] I would vote for Rob Garagiola. I think he’s a good person, and I think he’s been a very effective state senator, and he’s cast difficult and courageous votes,” O’Malley said. “I think he would be an excellent congressperson.”

Delaney’s poll, conducted by Fred Yang of Garin-Hart-Yang Research Group, shows him leading Garagiola, 49 percent to 23 percent, with 10 percent backing Pooran and 16 percent undecided. The survey was conducted March 26-27, and another poll by the same firm, conducted a week earlier, gave Delaney a 41 percent to 24 percent lead.

The latest poll also shows Delaney with a 53 percent positive, 18 percent negative rating among likely voters, while Garagiola has a 35 percent positive, 25 percent negative score.

The Garagiola campaign had not provided comment in response to the poll as of this posting.

Accurately polling primary contests can be difficult, given that turnout next Tuesday is expected to be low. Both surveys included 400 registered Democrats who said they were likely to vote in the primary.