By Greg Giroux, CQ Staff

Kentucky Republican Erwin Roberts is officially ending his campaign to unseat freshman Democratic Rep. John Yarmuth in the Louisville-based 3rd District. Roberts, a lawyer and former state official, had put his campaign “on hold” one day earlier after learning that his U.S. Army Reserves unit almost certainly will soon be called into active duty.

In a statement issued by his campaign Thursday afternoon, Roberts said he would not file the requisite paperwork with Kentucky election officials to qualify for the May 20 primary election. With the candidate filing deadline coming up on Jan. 29, Roberts needed to make a definitive statement about his political plans.

“Given the immediate and strong interest of other candidates to consider the race, I feel this clarity from my campaign will allow the party to have the opportunity to nominate a strong, viable candidate,” said Roberts, who launched his campaign against Yarmuth last May and was one of the most prominent African-American candidates recruited by Republican officials to run for the U.S. House in 2008. There are no African-American Republicans currently serving in Congress.

With Roberts now officially sidelined, former five-term Rep. Anne M. Northup stands out as the Republican who party officials in Louisville and Washington consider their strongest and most viable potential candidate. Northup lost her seat to Yarmuth by a margin of 2.4 percentage points in the strong Democratic election year of 2006. But she had previously succeeded in winning a series of elections in the Democratic-leaning district from 1996 through 2004, aided by her ability as an Appropriations Committee member at channeling federal money to her district, even though she held strongly conservative views on most issues.

Northup ran for governor in 2007, losing a primary challenge to Republican Gov. Ernie Fletcher , whose term in office was tarnished by ethics controversies. Fletcher was trounced last November by Democratic challenger Steven L. Beshear. Roberts, though he had previously served as a high-ranking aide to Fletcher, endorsed Northup in her primary challenge.

Republican Bob DeVore Jr., a political novice, has filed for the race. Yarmuth, who also has filed his candidacy paperwork, almost certainly will be unopposed in the Democratic primary.