A prominent Republican strategist on Tuesday endorsed Democrat Terry McAuliffe for governor of Virginia over the GOP candidate, state Attorney General Ken Cuccinelli.

Boyd Marcus, a former chief of staff to Republican Gov. Jim Gilmore and an adviser to current Virginia Lt. Gov. Bill Bolling, R, said he would advise McAuliffe for the remainder of this year's gubernatorial election.

"I’ve never before supported any Democrat, but this election Terry is the clear choice for mainstream conservatives," Marcus said in a statement released by the McAuliffe campaign. "I am excited to work with him to grow the already-long list of prominent Republican leaders who are supporting his campaign. Virginia is facing tremendous economic headwinds and we need a governor who is going to work with both parties."

Marcus also enjoys close ties to House Majority Leader Eric Cantor, R-Va., having served as the Virginia congressman's chief of staff in 2002.

"Virginians are concerned about each candidate's vision for the future and how they plan to grow the economy and create jobs, not who their political consultants are," said Cuccinelli spokesman Richard T. Cullen. "Ken Cuccinelli has a long and distinguished record of leadership and service in Virginia and has laid out substantive plans that will make the Commonwealth stronger. Terry McAuliffe, meanwhile, has been exposed as a failed job creator who has misled Virginians at every turn about his business record."

An outspoken conservative Cuccinelli's work to cull support from the Republican grassroots helped discourage Bolling from challenging the attorney general for the GOP gubernatorial nod. Most importantly, Cuccinelli managed to switch the nominating process from a primary to a convention, in which conservative activists (who favored Cuccinelli) are more influential.

Bolling had mulled waging an independent bid, but ultimately declined, citing the difficulty and high costs of doing so. Since then, Bolling has been complimentary of McAuliffe at key points during the campaign, seeming to undercut the notion of a unified Republican Party in Virginia.