Albuquerque Mayor Martin Chavez, a Democrat, will run for the seat being vacated by retiring Republican U.S. Sen. Pete Domenici, the Associated Press has learned.

Chavez, who would be the highest-profile Democrat thus far to enter the 2008 race, will announce his candidacy at a news conference Tuesday, according to a source close to the campaign who sought anonymity so as not to pre-empt the mayor's formal announcement.

The seat was thrown wide open with Domenici's announcement last week he would not seek re-election because of his health.

Chavez, an Albuquerque native, is in his third, nonconsecutive term as mayor. He served four years in the state Senate, and was the Democratic nominee for New Mexico governor in 1998. He lost to Republican incumbent Gary Johnson.

On the GOP side, U.S. Rep. Heather Wilson is the best known of the candidates seeking Domenici's seat. She announced her candidacy last week.