Democrat Ron Barber has won a special election in Arizona to finish the term of a congresswoman who was wounded in a mass shooting last year.

Barber, who was an aide to former Democratic representative Gabrielle Giffords, defeated Republican Jesse Kelly in Tuesday's election.

Giffords resigned her seat in the House of Representatives this past January to focus on her recovery from the near-fatal shooting, which occurred during a public appearance in Tucson in January 2011. Six people were killed and 13 others injured, including Barber. He will have to run for re-election in November for a full two-year term.

The special election to fill Giffords's seat was one of many elections being held across the country Tuesday, many of them congressional primaries to pick the Democratic and Republican candidates to run in November. One of the biggest races took place in Virginia, where former U.S. senator George Allen defeated little-known opponents in the Republican primary in the race for his old Senate seat.

Allen, a former governor of Virginia, lost his 2006 re-election bid to Democratic challenger James Webb after he was caught on camera using a racial slur to describe a Webb campaign volunteer. He will face Democrat Tim Kaine, another former Virginia governor, in the November election to replace the retiring Webb.

Primary elections were also being held in Maine, Nevada, North Dakota, and South Carolina.

In another election-year issue, officials in Washington state say a referendum on same-sex marriage will be placed on the November ballot.

Earlier this year, Governor Christine Gregoire signed legislation that legalized same-sex marriage, but it was put on hold while opponents gathered enough signatures to place it on the ballot. State election officials say opponents turned in nearly 250,000 signatures, will over the legal minimum of 120,577.

A recent poll shows more than 50 percent of Washington state voters approve of legalizing same-sex marriage.