The mayor of Anchorage plans to run for the Senate seat held by Ted Stevens since 1968, he said Sunday, ending months of speculation.

Mark Begich, a 46-year-old Democrat, said he plans formal announcements Monday in Anchorage and Fairbanks.

Begich has been considering taking on the longtime Alaska Republican since fall, when he met with Democratic members of the Senate. He eventually turned to voters for their thoughts in visits around the state and said it was time to formally establish the campaign.

"Coming off all the visits I took, it told me the state is ready for a change, ready for new ideas," Begich told The Associated Press. "There was really no single moment."

Stevens' camp did not immediately return messages Sunday, but the National Republican Senatorial Committee predicted Stevens would prevail.

"This does not change the strong support Sen. Stevens will receive from voters in this election," said Rebecca Fisher, the NRSC's spokeswoman. "We fully expect him to be re-elected this November."

Stevens filed in February for re-election. The 84-year-old Republican is popular in Alaska, with the state's largest airport bearing his name, but his legacy was tarnished last year when the FBI and IRS raided his home. Democrats consider him a prime target.

Sunday's news gave the state's Democratic party the boost it had hoped for in a state whose political climate has been darkened by scandal statewide and in Washington, D.C.

Three former Republican state lawmakers have been convicted on federal bribery charges; one more awaits trial.

Since last May, when the state lawmakers were charged, the party believed it saw an opening to take seats, and with that, possibly some power from the Republicans.

Begich is one way at breaking things open for the party, said Patti Higgins, who chairs the Alaska Democratic Party.

"I'm pleased. It's time to get on with the show," Higgins said. "He will restore Alaska's reputation.

Begich wasn't an official candidate when the NRSC began questioning his credentials in a Web site, www.begichbaggage.com.

Not to be outdone, last year the Alaska Democratic Party posted its own Web site aimed at Stevens. It's called www.retireted.com.

Begich's decision is backed by an aggressive push from top Democrats for him to challenge Stevens, the longest-serving Republican in Senate history and the target of a federal investigation.

Begich took several trips to Washington in recent months and was courted heavily by Democratic leaders.

He visited with Senate Majority Leader Harry Reid of Nevada, Senate Finance Chairman Max Baucus of Montana, and Sen. Chuck Schumer, chairman of the Democratic Senatorial Campaign Committee.

Begich then set out to hear from voters by forming an exploratory committee. He spent the last eight weeks traveling around the state to meet with Alaskans.

Stops included Fairbanks and Juneau, the state's capital, plus some of the state's far flung areas such as Bethel and Kotzebue.

Begich said the key concerns were rising energy costs, especially for those living in rural areas or away from road systems connecting small towns to largest cities.

He said he also heard repeatedly from military veterans concerned about receiving the proper care and benefits after their service ends.

Begich said voters are "feeling the pressure personally, but also feeling frustrated at Washington, D.C., to understand the concerns of everyday people."

Begich is the son of Nick Begich, who was representing Alaska in the House when his plane disappeared over the Gulf of Alaska in October 1972.

Federal authorities are reviewing the remodeling of the Stevens' official residence in Girdwood, a resort town south of Anchorage.

A former oil field executive has testified in a federal corruption trial that he sent company employees to work on the house.

Stevens hasn't been charged nor has he commented on the investigation other than to say he has paid all bills presented to him.