Mitt Romney’s weakness as a presidential candidate in Virginia so far threatens to derail the political ambitions of the state’s two most prominent Republicans, Gov. Robert F. McDonnell and U.S. Senate candidate George Allen.

If Romney loses the state next month to President Obama, as recent polls suggest he will, the negative fallout would be considerable for top GOP politicians in the Old Dominion.

A Romney defeat in Virginia would spoil McDonnell’s reputation as the politician who revived the state GOP, starting with his landslide election in 2009.

It probably also would mean that Allen would lose his second straight U.S. Senate race, this time to fellow former governor Timothy Kaine (D). Independent analysts note that Allen’s poll numbers have been moving in line with Romney’s.

“Allen declined in lock step with Romney. When Romney went down, Allen went down,” said Bob Holsworth, a retired political science professor who is now a partner in the Richmond public-service consulting firm DecideSmart.

The Virginia GOP has time to turn it around, of course. Romney’s strong performance in the first presidential debate on Wednesday evening might have been a start. (Almost all of this column was written before the debate.)

The Democrats’ advantage also is small, according to some polls. Both parties say the races remain up for grabs. They predict intense, street-by-street efforts by both sides to mobilize supporters.

Still, assuming the surveys are correct, Obama’s edge for now in Virginia is ominous for the GOP.

For McDonnell, a presidential defeat in Virginia would tarnish his record as the man who stopped the surge of Democratic victories in the state from 2001 to 2008. First, he led the GOP to the 2009 sweep of the offices of governor, lieutenant governor and attorney general. Then he led it to pick up three U.S. House seats at the Democrats’ expense in the 2010 congressional elections and to take back effective control of the state Senate in 2011.

The popular governor has put his formidable political organization to work on Romney’s behalf. He also has a personal interest in the race: If Romney loses at the national level, McDonnell has no chance of getting a Cabinet post, like attorney general, either before or after he’s forced to leave the governorship in early 2014. (Virginia governors, by law, cannot serve consecutive terms.)

A Romney defeat would also revive criticism that McDonnell should have done more to curb the Virginia GOP’s appetite for restricting abortion rights.

The Republicans are on the defensive partly because the gender gap — in which Democrats have a sizable advantage among women — is growing.

The gender gap results partly from differences between the sexes over economic policies and health care. Abortion rights are also part of the divide, however, and nowhere more than in Virginia in the past year.

The state attracted national attention when the GOP-controlled legislature pushed through a requirement that women desiring abortions must first have an ultrasound.

“Democrats have inundated voters with messaging about the GOP-led ultrasound initiative, and they have tied Romney to the social right’s unpopular policies,” said Mark Rozell, a public-policy professor at George Mason University.

The Democrats’ current advantage in the polls might seem surprising, given that they lost three straight statewide elections from 2009 through 2012.

One big reason explains the apparent discrepancy, however, and points to why turnout is so critical in the state this year.

A lot more people vote in Virginia in presidential years than in other years. And the people who show up only in presidential years are disproportionately Democratic, according to independent observers.

For example, turnout was 74 percent in 2008. That was when Obama became the first Democrat to carry Virginia since 1964. Turnout plunged to 44 percent in 2010. Republicans won big in the congressional races.

The every-four-years voters tend to be nonwhite, lower-income and younger — all groups that usually break for the Democrats. Ensuring that they turn out this year is a top priority for the Obama and Kaine campaigns.

“You have two entirely different electorates,” Holsworth said. “Obama and Kaine have to have this larger electorate [to win]. They’re going to need to get the intermittent voters to the polls.”

Virginia Democrats remain concerned that something unforeseen could change the dynamic. One party strategist listed his worries as a debate gaffe, a stock market plunge or a foreign crisis.

Barring any of that, however, the Democrats’ “presidential majority” in Virginia currently looks likely to reverse the GOP’s three-year winning streak. And McDonnell and Allen could well be looking for new career paths.

I discuss local issues Friday at 8:50 a.m. on WAMU (88.5 FM). For earlier columns, go to