Joe Lhota is now without one of his most faithful supporters — his dog, Harmony.

The GOP mayoral candidate’s 15-year-old black Lab had to be put down Monday.

“Losing Harmony was really hard . . . My daughter and Harmony grew up together,” he said yesterday. “She followed me around everywhere — I think it had something to do with the fact that I drop food when I eat.”

Lhota still made it to a Republican forum on Monday night in Borough Park, Brooklyn, but was clearly upset.

Afterward, he tweeted, “I’m so sorry you didn’t get a chance to run on the Gracie Mansion lawn. XXXOOO.”

The family also has a yellow Lab, Lindy, and in June, Lhota tweeted pictures of him walking the dogs along the Brooklyn Heights Promenade.

The GOP front-runner said his now-college-age daughter, Kathryn, was beside herself over the loss of Harmony.