Updated: 6:16 p.m.

Former Arizona state Sen. Jonathan Paton announced today that he will run for the Republican nomination in the state’s 1st district.

If Paton wins the GOP primary, he will likely face former Rep. Ann Kirkpatrick, who has had a great deal of Democratic enthusiasm behind her attempt to recapture her old seat. In his announcement to supporters, Paton hit her on that point.

According to Paton, Washington Democrats “are already filling her campaign coffers,” and her “major donor list reads like a Who’s Who of Liberal America — Nancy Pelosi, Anthony Weiner, EMILY’s List, Big Labor, and radical environmentalist groups have all written big checks.”

Kilpatrick raised about $200,000 in the fourth quarter and had almost half a million dollars in the bank as of Dec. 31.

Paton ran for Congress in 2010 in the 8th district, based in Tucson. He lost the GOP primary to veteran Jesse Kelly. Kelly went on to lose in a close race against Rep. Gabrielle Giffords (D).

Kelly will announce soon that he is running for the GOP nomination in the race to replace Giffords, whose resignation is effective today.

Both parties consider the 1st district, which sprawls across the eastern part of the state, a tossup. It is an open seat since Rep. Paul Gosar (R) opted to run in the more Republican 4th district following redistricting.

Other Republicans mentioned as potential candidates are former state Rep. Bill Konopnicki and Arizona Corporation Commission Chairman Gary Pierce.

The Democratic Congressional Campaign Committee sent out a press release noting that Paton lobbied on behalf of payday lenders and that he does not currently live in the 1st district.

“Arizona voters in the Eighth District rejected Jonathan Paton in 2010, and voters in the First Congressional District won’t trust a lobbyist carpetbagger in 2012,” DCCC spokeswoman Amber Moon said.

Kirkpatrick is perceived as having the inside track on the Democratic nod. She does have a primary opponent in attorney Wenona Benally Baldenegro. Baldenegro is considered a potential rising star and could rally Native American support in the district, but her third-quarter fundraising was lackluster.