Virginia state Del. Bob Marshall (R-13th) confirmed on Thursday that he is planning to seek the GOP nomination in the U.S. Senate race.

Marshall said in a brief phone interview that he would officially announce his candidacy "soon" though he did not give a timeline, simply saying it won't be this week. He said he has not decided yet about where he would like to kick off his campaign.

The Manassas resident is in Richmond today on the second full day of the 2012 General Assembly session. Marshall, who lost the GOP nomination to former Gov. Jim Gilmore (R) in 2008 for the seat eventually won by Sen. Mark Warner (D), is actively collecting signatures to make him an official candidate in the primary, which is set to be held on June 12.

He will likely campaign heavily on social topics from an ideologically conservative point of view as he's previously indicated that he thought the race has not focused enough on issues like abortion and gay rights.

Four GOP candidates are already in the race. Former Sen. George Allen (R) of Mount Vernon is the favorite to win. He served as governor in the mid-1990s before defeating former Sen. Chuck Robb (D) in 2000 to win a seat in the upper chamber of Congress. Allen lost his re-election bid in 2006 to Sen. Jim Webb (D), who is retiring.

Also running for the Republicans are Tea Party activist Jamie Radtke (R) of North Chesterfield; attorney David McCormick (R) of Virginia Beach and Faith Exodus Ministries Bishop E.W. Jackson (R) of Chesapeake.

In the Democratic primary, former Gov. Tim Kaine (D) of Richmond, who last served as Democratic National Committee chairman, faces Marine Corps veteran Courtney Lynch (D) of Fairfax and brain injury advocate Julien Modica (D) of Reston.