Were it not for the Republican National Convention, today's Arizona primary would be garnering much more attention, as redistricting led to some of the wildest primaries of the cycle, including one Member-vs.-Member clash.
The results will offer resolution to nearly a year of competitive House and Senate primaries. At least one Member will find out tonight that he will not be returning to Capitol Hill next Congress, and the table will be set on races that Democrats and Republicans in Washington, D.C., will be paying close attention to this fall.
In Oklahoma, Democrats and Republicans are vying for their party's nominations in the 2nd district, with runoffs set today to determine the November race to replace retiring Rep. Dan Boren (D).
The early GOP frontrunner, Rep. Jeff Flake, appeared to have a competitive primary on his hands, thanks to a self-funded bid from real estate investor Wil Cardon.
Much of Cardon's television advertising was highly negative against Flake. But in early August, Cardon surprised many when he scaled back his television advertising. As soon as the news broke, one Flake source wrote in an email, "Put a fork in him."
The timing of the Cardon fade was crucial. Flake wasted no time preparing for the fall campaign against the presumptive Democratic nominee, former Surgeon General Richard Carmona.
The Cardon rivalry meant that Flake had to spend resources and consolidate the right. Democrats are quick to point out that while Flake should win tonight by a healthy margin, the primary delayed his ability to prepare for the fall.
Arizona's 4th district
Rep. Paul Gosar (R) moved from the competitive 1st district to the newly drawn 4th district, which covers most of western Arizona and is a Safe Republican seat.
At first, he faced a three-way primary against state Sen. Ron Gould and Pinal County Sheriff Paul Babeu. Babeu had begun to achieve national celebrity as a future GOP star, but his campaign imploded amid a scandal involving an ex-boyfriend's immigration status.
Public polling has been scant. In a late July interview with Roll Call, Gosar expressed confidence about his prospects. Some Republicans remain skeptical, though, because his television presence has lagged behind the Club for Growth's ad campaign for Gould.
In typical fashion, the Club for Growth has been merciless in its attacks against Gosar. One unaligned GOP strategist said that if Gosar loses this race, "full credit, without question," should go to the club.
But Gosar has had allies of his own. He defeated then-Rep. Ann Kirkpatrick (D) in a tough 2010 fight. His primary that year was competitive, and many credit a Sarah Palin endorsement as the reason he won his nomination. Palin endorsed again this cycle, albeit almost too late to register in early voting.
Arizona's 5th district
Former Rep. Matt Salmon (R) is widely expected to win this primary and as a result return to Congress in the fall.
But his primary rival, former state Speaker Kirk Adams, has unleashed a fascinating barrage of endorsements in the final weeks of the campaign. Palin even trekked to Arizona to campaign for Adams on Monday.
Salmon is seeking to return to Congress after a 12-year sabbatical to honor a 1990s term-limit pledge. Salmon has strong name identification, the Club for Growth behind him and the financial edge.
This seat most closely resembles Flake's current district. Flake endorsed Adams last week.
Arizona's 6th district
This is the race to watch tonight.
It took a while, but the primary for the new 6th district is among the nastiest Member-vs.-Member contests of the cycle.
Because freshman GOP Reps. Ben Quayle and David Schweikert share solid conservative voting records, the campaign has focused on the personal. The accusations have been vicious and relentless.
Most unaligned operatives in the state, and national handicappers, predict Schweikert will come out ahead. Still, one national Republican cautioned that Quayle has a team that is especially adept at getting out the vote.
Before this Member-vs.-Member race came to be, both Members were talked about as future Senate candidates.
Arizona's 9th district
Races elsewhere in the state have overshadowed what will be a fall tossup race, and Democrats are energized.
But there is little consensus on either side as to who will win today's primary.
An unscientific gut check of Arizona Democrats says that former state Sen. Kyrsten Sinema has the best chance of winning their party's nomination. Still, she has had stiff competition in her primary. One Democratic strategist has gone so far as to call the crowded field "an embarrassment of riches."
Former state party Chairman Andrei Cherny is also in the hunt for the nomination, and he has the valued and effective endorsement of Bill Clinton. State Sen. David Schapira has run an underfunded but respected campaign.
On the Republican side, most have assumed former Paradise Valley Mayor Vernon Parker will win, but the GOP field is crowded and underfunded. Like the Democratic side, public polling is scant, so anything could happen. Other contenders are ex-Chandler City Councilman Martin Sepulveda, businessman Travis Grantham and retired Air Force officer Wendy Rogers.
Oklahoma's 2nd district
In two primary runoffs, seed company owner Wayne Herriman and former District Attorney Rob Wallace are seeking the Democratic nomination, and plumbing company owner Markwayne Mullin and state Rep. George Faught are facing off for the GOP nod.
The 2nd district includes reliable GOP territory, and Roll Call rates this race as Leans Republican.