Virginia is one of four tight Senate races taking place in presidential battleground states. Obama and Republican challenger Mitt Romney are jamming the airwaves with ads and building deluxe voter-turnout campaigns that will influence races down the ballot. Tim Kaine (D) and George Allen (R), both former governors, have been locked in a match so tight that there was, until recently, no daylight between them. (Mr. Kaine opened up a single-digit lead in a pair of recent surveys.)
Virginia is "the Senate race in the country that gets decided by the presidential" political picture, says Jennifer Duffy, the Cook Political Report's analyst on Senate contests.
The presidential race is also expected to affect Senate battles in Ohio, where Sen. Sherrod Brown (D) is up for reelection against state Treasurer Josh Mandel (R); in Florida, where Sen. Bill Nelson (D) is defending his seat against Rep. Connie Mack (R); and in Nevada, where Sen. Dean Heller (R) is up against Rep. Shelley Berkley (D). So far, polls show the three incumbents leading.