Virginia Republican Corey Stewart, the chairman of the Prince William County Board of Supervisors, said Monday he's "seriously considering" a run for Senate in 2012, which would likely pit him against former Sen. George Allen (R-Va.) in a primary. 

In an interview Monday on NewsChannel 8, Stewart said he was certain Allen will enter the 2012 race, and admitted that the former senator is the clear frontrunner. 

But in an early signal that Stewart may be ready to wage a primary challenge to Allen, he labeled Allen's single term in the Senate as "mediocre" and warned that the former senator shouldn't count on the Republican base to fall in line behind him in two years. 

"Sen. Allen was a great governor. He really was," said Stewart. "But his record in the Senate was mediocre. And I don't think that most people in Virginia think of him as a good senator. They think of him as a great governor."

Stewart, who said he plans to make a decision on whether or not to jump in the race within a year, said Allen could find that a lot of his base has "moved on" since his last run in 2006. 

"He's going to have a tough time," Stewart concluded.     

Earlier this month, the state GOP opted for a primary over a party convention to choose their Senate nominee in 2012 — a move that was widely seen as a tacit endorsement of Allen. The former senator's high name recognition and strong fundraising ability make him the prohibitive favorite in a primary. 

A convention process, which the party used in both 2008 and 2009, would offer a lesser-known or more staunchly conservative candidate greater ability to make a run at Allen by piecing together enough support among party insiders to capture the nomination.

Stewart's warning echoes what former Rep. Tom Davis (R-Va.) said last week — a primary helps Allen initially, but it's no slam dunk.

"There are a lot of variables to this thing," said Davis, who decided to forgo a Senate bid in 2008 after party insiders decided against holding a primary. Former Gov. Jim Gilmore (R-Va.) became the nominee and lost badly to Sen. Mark Warner (D-Va.).

"Initially, it definitely helps Allen," Davis said, noting that it immediately discourages some long-shot candidates from even waging a bid. "But a year is an eternity in politics and this thing hasn't even started to develop yet."