RepublicansÂ need a net gain of four seats in November to take control of the U.S. Senate.
Besides Virginia, voters in Maine, North Dakota and Nevada were picking Senate candidates in contested primaries on Tuesday.
Allen, once a rising star on the national political stage who stumbled in his 2006 re-election bid on the issue of race, took 65 percent of the vote. Jamie Radtke, the strongest of his three rivals, trailed with just over 23 percent.
Allen and Kaine both enjoy significant fundraising capability, well-established campaign networks and national prominence. Allen weighed a presidential run four years ago. Kaine was an early backer of PresidentÂ Barack ObamaÂ and later served as Democratic National Committee chairman.
Virginia is considered a tossup in the 2012 presidential election, ensuring the Allen-Kaine campaign will carry added significance.
In Maine, voters were picking candidates for the open U.S. Senate seat being vacated by RepublicanÂ Olympia Snowe, who is retiring.