Kentucky Gov. Steve Beshear (D) endorsed his lieutenant governor, Daniel Mongiardo (D), this afternoon in what is expected to be a hotly-contested Senate race in 2010.

Mongiardo announced he would challenge Sen. Jim Bunning (R-Ky.) earlier this year, but he isn’t expected to have a clear shot at winning the Democratic nomination. Attorney General Jack Conway (D) is expected to throw his hat into the ring, perhaps in a matter of days.

“While I will miss the contributions that Daniel has brought to our team, I know he feels called to service in the U.S. Senate and I support his mission,— Beshear said of Mongiardo.

“I am deeply honored and proud to have Governor Beshear’s strong endorsement and look forward to having his support throughout this campaign,— Mongiardo said in a statement. “The Governor has been a trusted mentor and partner whose steady hand and strong leadership has served our Commonwealth well during these difficult times.—

Conway’s camp downplayed Beshear’s announcement Friday afternoon.

“People will have to decide for themselves whether a tepid statement honoring a long-standing political commitment, done on a Friday afternoon while the governor is out of town is indeed newsworthy,— said Conway consultant Mark Riddle. “Most expected the governor would have to say something on his running mate’s behalf.—

Mongiardo, then a state Senator, came just two points shy of defeating Bunning in a hotly contested race in 2004. Bunning has said he is running for re-election, despite pressure from within the ranks of his party to step aside to make room for a stronger nominee.