TUCSON, Arizona (CBS News) -- The race to replace retired Rep. Gabrielle Giffords will kick into full gear after today, when Republicans choose their candidate in a special election primary.
There are four Republicans on the ballot in today's Arizona primary. The winner will face off in a June 12th special election against Democrat Ron Barber, Giffords' former district director, who is uncontested in today's primary.
Giffords, a three-term Democrat who represented Arizona's eighth district, stepped down from Congress in January, just over a year after she was shot in the head in a mass shooting. Giffords has endorsed Barber -- who was also injured in the 2011 shooting -- in the race to replace her.
The Republicans hoping to compete against Barber are: State Sen. Frank Antenori, construction manager and former Marine Jesse Kelly, retired Air Force pilot Martha McSally and University of Arizona broadcaster Dave Sitton.
The special election is likely to be competitive. Giffords narrowly won re-election in 2010, and the southeastern district, which covers part of Tucson and a section of the U.S.-Mexico border, is splintered between Democrats and Republicans. Arizona overall traditionally votes Republican, but President Obama's re-election team thinks the state could be more competitive this year.
The Tucson shooting that left Giffords severely wounded spurred many lawmakers and citizens to call for more civility in politics, and Barber has promised he won't run personal attack ads in his campaign, the Arizona Republic reports.
With $550,000 in the bank for his campaign, Barber has the cash to defend himself against any Republican attacks --which have already started. The Arizona Republican Party has already spent more than $111,000 on media like mailers and robocalls to attack Barber, the Arizona Daily Star reports, accusing him of supporting cuts to Medicare and higher energy prices.
While the winner of the June 12 primary will replace Giffords for the rest of her term, the candidates will also have to campaign for the newly-drawn second district if they plan on serving past this year.
Barber is uncontested in today's primary, but he currently faces two opponents in the Democratic primary in the new District 2. That primary falls on August 28th.