In a highly unusual set of circumstances, four Arizona Republican House Members face serious primary challenges today, with freshman Rep. Trent Franks widely regarded as the most endangered.

Franks faces radio executive Rick Murphy in the northwestern Arizona 2nd district, a Republican stronghold that he won by securing the GOP nomination in 2002 by just 797 votes. The increasingly nasty race has largely broken along ideological lines.

Murphy has stayed competitive with Franks throughout the contest on the financial front, thanks to $550,000 worth of personal loans to the campaign.

“We have been able to set the agenda of the race,” said Murphy media consultant Michael Shannon. “It is about Franks’ inability to keep his promises.”

Franks did not respond to a call seeking comment.

Elsewhere in the state, Rep. Jim Kolbe (R) faces a challenge from conservative state House Majority Whip Randy Graf in the southern Arizona 8th district, while Rep. Jeff Flake (R) is being opposed by former state Sen. Stan Barnes in the suburban Phoenix 6th district. In the neighboring 5th district, Roselyn O’Connell, the former chairwoman of the National Women’s Political Caucus, is taking on Rep. J.D. Hayworth (R).

Freshman Rick Renzi (R) has escaped without a primary in the 1st district but is seen as one of Democrats’ top targets in the fall. He will face former Flagstaff Mayor Paul Babbitt (D) in November.

Nevada voters will also go to the polls today, to select a Republican challenger to Senate Minority Whip Harry Reid (D) and challengers to the state’s three House incumbents. None of these primaries is expected to be particularly competitive.

But in Arizona, state observers acknowledge the rarity of having so many credible primary challengers, considering that since the state’s founding in 1912, only five incumbents of either party have been defeated in primaries.

Rather than detecting an overarching statewide trend, however, strategists say each primary has its own unusual set of circumstances.

Flake, for instance, has pledged to serve just three terms, a promise that will come due in 2006. Barnes, who previously ran unsuccessfully for Congress in 1992, is likely using this race to build name identification district-wide for a possible open-seat race next cycle.

Similarly, O’Connell may be positioning herself for a second run in the 5th district in 2006 if, as is widely speculated, Hayworth decides to challenge Gov. Janet Napolitano (D).

In Franks’ case, his first re-election bid following a narrow primary win in 2002 makes him an extremely attractive target for ambitious Republicans.

The odd-shaped 2nd district takes in much of the northwest corner of the state, with two arms snaking through the Hopi Indian Reservation in the north and the Phoenix suburbs in the south.

More than 80 percent of the district’s population lives in the Phoenix suburbs, making it a solidly Republican seat where President Bush took 56 percent in 2000. The likely Democratic candidate is 2002 nominee Randy Camacho.

Murphy, who owns five radio stations in the district, began his campaign in March with a pledge to spend up to $1 million of his own money to unseat Franks. He seems unlikely to meet that earlier pledge but has given himself enough money to stay at parity with Franks.

In fact, through Aug. 18, Murphy had a decided cash-on-hand edge with $380,000 in the bank to Franks’ $137,000.

Although Franks gave himself $300,000 in his 2002 race, he has yet to make a similar donation this time around.

To this point, Murphy has largely dictated the terms of the contest, taking to Phoenix broadcast television to promote a message that Franks does not keep his word.

Murphy has attacked Franks on his decision to accept money from political action committees after pledging not to do so last cycle, and for his reversal on the Medicare prescription drug bill in 2003. Franks originally opposed the bill but switched his vote under pressure from the White House and Congressional leaders. The measure ultimately passed 220 to 215.

Murphy is currently up with an ad touting his endorsement by The Arizona Republic.

As he did in 2002, Franks has run a largely unorthodox campaign, relying on targeted radio advertising and direct mail to reach voters.

He has decried Murphy for running a negative campaign, a charge that Shannon rejects.

“If you tell a Congressman he has a stain on his tie, he says it’s a vicious personal attack,” Shannon said.

In this contest, Franks seems likely to rely on the same base of abortion rights opponents and Christian conservatives that delivered him a narrow 28 percent to 26 percent win in the 2002 GOP primary.

In that race, Franks was not initially seen as a top-tier candidate to replace Rep. Bob Stump (R), who was retiring after 13 terms.

Stump had endorsed his longtime chief of staff, Lisa Atkins making her the prohibitive favorite in the Republican primary. Franks, however, eked out a 797-vote victory over Atkins, and then cruised to a 60 percent to 37 percent win over Camacho in the fall.

While Franks appears to be the only incumbent in truly serious jeopardy of losing on today, the race in the 8th district between Kolbe and Graf has also drawn considerable attention.

Kolbe has put together a largely moderate voting record during his 20 years in the House but faces a serious challenge from Graf, who calls the Congressman too liberal on immigration issues and says his pro-abortion rights stance is out of step with the district.

The two also differ on a federal amendment banning gay marriage. Graf supports such an amendment while Kolbe, the only openly gay Republican Member of Congress, opposes it.

A former golf pro, Graf has run an extremely aggressive campaign but has raised almost no money, making an upset of Kolbe a long shot.

As of Aug. 18, Graf had raised just $27,000 for the race with $20,000 on hand. Kolbe had raised $833,000 in the cycle to date with a hefty $559,000 left in the bank.

Kolbe has also brought together strange bedfellows in his campaign, receiving the endorsement of both the Club for Growth, a leading voice in the conservative movement, and the Republican Main Street Partnership, which backs moderate candidates.

Meanwhile, in Nevada, the most active primary fight is the one for the right to become the GOP Senate nominee.

Six men are vying for the right to take on Reid, the heavy favorite.

Leading the pack of relative unknowns is Richard Ziser, who probably has the highest name recognition thanks to his leading role in the state’s successful ballot initiative banning gay marriage.

Ziser’s campaign seems to be based primarily on contrasting his opposition to gay marriage with Reid’s opposition to a Constitutional amendment barring such unions.

Prominently displayed on Ziser’s campaign Web site is a box that reads “who does Harry Reid represent?” and then becomes a link to the Human Rights Campaign, a group that supports equal rights for gays and lesbians. The link takes visitors to the group’s Web page, where it says Reid has earned a 100 percent rating from the Human Rights Campaign and seeks contributions for Reid’s campaign.

A former GOP legislative Senate aide named Royle Melton is also on the ballot.

Melton served former U.S. Senators Chic Hecht and Paul Laxalt, both Republicans, in their Washington offices.

Also running are four unknowns, some of whom hold conspiratorial and bigoted beliefs.

For instance, Florida resident Robert Brown told the Las Vegas Review-Journal that nuclear waste is already being dumped at Yucca Mountain, 100 miles northwest of Las Vegas, “under the cover of darkness.”

Kenneth Wegner says the Mexican border needs more protection to weed out immigrants who are “disease free and want to be citizens” from ones who come to the United States solely to “rape our country, go on welfare and get your kids a free lunch.”

Also running are garbage truck driver Carlo Poliak, who now goes by just Poliak, and Cherie Tilley, who boasts of having played high school football with Vice President Cheney in Casper, Wyo.

Whoever wins faces a daunting task as Reid has almost $5 million in the bank. His closest competitor, Ziser, has only about $33,000 cash on hand.

In the House contests, Rep. Shelley Berkley faces two challengers in the 1st district Democratic primary, though she is expected to win easily.

Six Democrats are vying for the right to challenge Rep. Jon Porter (R) in the 3rd, though former Park Place CEO Tom Gallagher is expected to win.

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