A once-in-a-generation opportunity for Democrats to grab a congressional seat in the heart of the Valley is quickly becoming one of the nastiest races of the 2012 cycle.

Sen. Frank Antenori, a Tucson Republican, is seriously considering dropping his bid for Congress and turning his full attention to re-election in the state Senate.

House Speaker Andy Tobin on Monday announced that he will forgo a run for Arizona’s new 4th Congressional District.

Sen. Steve Gallardo, a Phoenix Democrat and a fierce critic of SB1070, has been invited to testify during a Congressional subcommittee hearing about state-level enforcement of immigration laws. SB1070 architect Russell Pearce, whom Gallardo often clashed with when Pearce served in the Legislature, is also scheduled to testify at the hearing.

TUCSON a�� State Sen. Paula Aboud has withdrawn from the Congressional District 2 race and is endorsing former congressional aide Ron Barber for the seat.

Businessman and sports mogul Jerry Colangelo threw his support behind Vernon Parker, giving the former Paradise Valley mayor a coveted big-name endorsement as the Republican field in the 9th Congressional District continues to grow.

The intraparty war between congressional Republican leadership and the conservative Club for Growth appears to have simmered down for now, even while the race between U.S. Reps. David Schweikert and Ben Quayle is growing fiercer.

U.S. House Speaker John Boehner this week agreed to give Schweikert a contribution from his PAC to compensate for a contribution he made earlier to his primary rival Quayle.

Vernon Parker kicked off his campaign for Arizona’s 9th Congressional District with the aura of a frontrunner. In a race for a competitive but Democratic-leaning district, Parker is the only big name in the GOP primary so far. Heavyweights who were expected to get into the race such as Hugh Hallman, Steve Moak, Gary Pierce and Don Stapley have all opted out.

Ron Barber went from placeholder to full-fledged candidate, with an announcement today that he’ll seek a full term in Congress.

Paradise Valley Town Councilman Vernon Parker will make a “major announcement” on Wednesday and is expected to jump into the GOP primary for Arizona’s 9th Congressional District.