Tim Kaine effectively clenched the Democratic 2012 U.S. Senate nomination by being the lone Democrat to submit qualifying petitions.
Four Republicans, however, filed petitions bearing voter signatures in hopes of qualifying for the June 12 primary, heralding two hard months of campaigning for front runner George Allen.
They are vying for the seat of Democratic Sen. Jim Webb, who unseated Allen from the Senate in 2006 but is not seeking a second term.
Kaine submitted more than 30,000 signatures on petitions delivered to the State Board of Elections. Two Democrats who had established federal campaign committees, Courtney Lynch and Julien Modica, have both endorsed Kaine.
Allen tendered the most signatures of any Republican, nearly 27,000. Tea party leader Jamie Radtke presented 21,552, state legislator Bob Marshall submitted 17,133, and Chesapeake clergyman E.W. Jackson gathered 11,188.
Both parties will begin vetting and validating the petitions on Friday. To qualify for the primary ballot, candidates had to submit petitions bearing 10,000 registered voters' signatures, including at least 400 from each of Virginia's U.S. House districts.
While Kaine is free to spend the next several weeks raising cash for his fall election battle, Allen faces determined challengers from the right who accuse him of voting in his previous term to increase federal spending.
Radtke this week released her campaign's first online ad labeling Allen a "big-government, big-spending career politician."
Allen, like Kaine a well-connected former governor, held enormous monetary advantages over the rest of the GOP field through the end of 2011 as shown in the most recent campaign finance reports. The slightly more than $2 million Allen's campaign had on hand as of Jan. 1 was more than quadruple the cash held by all of his opponents combined.
Marshall, who joined the race in mid-January, confronts Allen with something no other Republican can claim: experience running a statewide nomination fight.
In 2008, Marshall came within a few delegate votes of winning the GOP senatorial nomination over another former governor, Jim Gilmore, in a statewide convention in Richmond. Gilmore was routed in the November election by Democrat Mark R. Warner.
Marshall is the General Assembly's most outspoken member on conservative social issues and sponsored the unsuccessful "personhood" bill in the 2012 session. The legislation, carried over into next year's session, would give full rights of personhood to human embryos from the instant of conception, effectively outlawing abortion in Virginia if the Supreme Court's 1973 decision legalizing the procedure is ever overturned.
The Associated Press contributed to this report.