LAS VEGAS — Republican Sen. John Ensign's announcement that he would not seek a third term could trigger a free-for-all contest to fill the Nevada seat coveted by Democrats and to win the helm of what will be a significantly reconstructed U.S. Senate, where eight members have now said they won't run again.
Ensign, who is under investigation by the Senate Ethics Committee, said he decided last week he would not pursue re-election to protect his family from "exceptionally ugly" campaign attacks.
The 52-year-old acknowledged in June 2009 that he had an extramarital affair with Cynthia Hampton, a former member of his campaign staff, and that he had helped her husband, Doug Hampton, a member of his congressional staff, obtain lobbying work with a Nevada company.
His decision to withdraw from the 2012 race after months of pledging to run did not immediately produce a wave of confirmed candidates. But while no one officially announced their intent to claim the seat, a handful of Republican and Democratic politicians declared an interest and assessed their chances at victory, paving the way for what could be a months-long political standoff.
Jennifer Duffy, a "Cook Political Report" senior analyst who recently declared Ensign the nation's most vulnerable incumbent, said Ensign's announcement Monday was good news for the GOP.
"It is still a competitive race, but what Republicans will probably avoid is a pretty nasty primary," she said. "It just clarifies things so much for them."
Sen. John Cornyn, R-Texas, chairman of the National Republican Senatorial Committee, said he has not talked to any potential candidates in the Nevada race for the Senate. He said he agreed with Ensign's decision to retire when his term ends.
"I think he made the right decision for his family," Cornyn told The Associated Press.
Ensign would likely have faced a tough primary challenge if he stayed in the race. Possible rivals included Rep. Dean Heller, Nevada Lt. Gov. Brian Krolicki or former Senate candidate Sharron Angle.
The general election fight could have been equally bruising, with popular Democrats Rep. Shelley Berkley, Secretary of State Ross Miller and Attorney General Catherine Cortez Masto all considered potential challengers.
With Ensign's exit, his former prospective rivals remain likely Senate candidates.
Angle, who lost to incumbent Senate Majority Leader Harry Reid in November, has hinted at a future run for office, but has not clarified which post she has her eyes on. She has traveled in recent months to Christian rallies in early-primary states South Carolina, New Hampshire and Iowa.
"Nevadans are thankful for his service, and I wish him well," Angle said of Ensign in a Twitter message Monday.
Her entry into the race could mark the second face-off between Heller and Angle since 2006, when she placed behind him in a Republican congressional primary.
Heller finished with 50 percent of the vote that year against Democrat Jill Derby's 45 percent. He won re-election with 52 percent of the vote in 2008, and his popularity soared in 2010, when he finished with 63 percent of the vote.
Of Ensign's announcement, Heller said Monday that "this must have been a very difficult decision for John to make."
Angle is popular among tea party groups, but could be vulnerable in a general election. National and Nevada Democrats collected a raft of controversial or embarrassing statements to use against her during her testy battle against Reid, and have expressed an eagerness to roll out their arsenal should she try again.
Angle, a former Nevada lawmaker who often slammed big government, was critical of federal entitlement programs such as Social Security.
The primary could attract other Nevada Republicans.
GOP consultant Ryan Erwin, of Las Vegas, issued an opaque statement on Krolicki's political ambitions minutes after Ensign's announcement.
"Today is not the day for any announcement on Lt. Gov. Krolicki's political future," the statement read. "In the coming days, he and his family will consider opportunities to best serve the people of Nevada."
National Democratic officials said Nevada was near the top of their target list for a Democratic win in the Senate next year.
"Whoever Republicans field as their candidate will have a tough time holding onto this seat in a blue-trending state with President (Barack) Obama at the top of the ticket," said Guy Cecil, executive director of the Democratic Senatorial Campaign Committee.
Berkley has emerged as the top candidate in that field. She said Ensign told her he would seek a third term as recently as two weeks ago.
She said she was weighing her options and could make an announcement soon.
"I am traveling up north more than I have been, obviously," said Berkley, of Las Vegas, indicating a desire to test the waters in conservative northern Nevada. "Overwhelmingly, people are urging me to run. I have told everyone that I am not going to rush into in this decision."
Adding to the round of political musical chairs are plans for Nevada's fourth congressional seat. The new post will be carved from the state's existing three congressional districts this year by the Nevada Legislature and the final boundaries could lure a handful of unexpected candidates.
Ensign is the eighth U.S. senator to announce he will not seek re-election. The others are Democrats Daniel Akaka, of Hawaii; Jeff Bingaman, of New Mexico; Kent Conrad, of North Dakota, and Jim Webb of Virginia. Republicans Kay Bailey Hutchison, of Texas, and Jon Kyl, of Arizona, also said they would not run, as did independent Joe Lieberman of Connecticut.
Ensign's admission that he cheated on his wife seemingly foreshadowed his political downfall. Amid the scandal, his parents provided the Hamptons with $96,000 described as a gift, and Ensign helped find Doug Hampton a lobbying job.
The Justice Department and the Federal Election Commission investigated, then dropped the cases with little explanation. The Senate ethics panel, however, recently named a special counsel to look into the matter.
Through it all, Ensign remained adamant that he would seek re-election until his announcement. He said it was difficult to give up the job he loved, but "I have learned through the mistakes I have made that there are consequences to sin."
Freking reported from Washington.
© Copyright 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.