(AP Photo/Lauren Victoria Burke)
Sources familiar with Blunt's intentions said he would announce his candidacy at a series of stops across Missouri. The sources spoke on condition of anonymity to avoid upstaging Blunt's announcement.
Blunt will start the day in St. Louis, followed by stops in Jefferson City, Carthage and Cape Girardeau.
Republican Sen. Kit Bond announced in January that he would not seek election to a fifth term. So far, Democratic Secretary of State Robin Carnahan is the only other candidate to enter the race.
Blunt, 59, has represented southwest Missouri in the House since 1997 and recently stepped aside as the House minority whip. He is a former high school teacher who served as Greene County clerk from 1973 to 1985.
He was elected Missouri secretary of state in 1984 at age 34 and served two terms before losing a bid for governor in a contentious 1992 Republican primary. He then spent several years as president of Southwest Baptist University in Bolivar, Mo., before running for Congress.
His oldest son, Matt Blunt, just ended a four-year term as governor in January.
The Missouri Senate race could become a showdown between two of Missouri's most prominent political families.
Carnahan is the daughter of former governor Mel Carnahan, who was killed in an October 2000 plane crash while campaigning for the Senate. He won anyway and his widow, Jean Carnahan, was appointed to the Senate seat. Robin Carnahan also is the sister of U.S. Rep. Russ Carnahan.
Both the Blunts and Carnahans have reputations as prolific fundraisers.
Republican and Democratic leaders both would like to avoid costly primaries for the open Senate seat from Missouri, which is expected to be among most hotly contested nationally as Democrats try to gain a filibuster-proof majority.
But former state treasurer Sarah Steelman, who lost a tough Republican primary last year for governor, also has been considering a Senate run.
Blunt scheduled a news conference for 9:30 a.m. today at Harris-Stowe State University in St. Louis.
State Rep. Ward Franz, chairman of the Missouri House Republican Caucus, said Blunt was to speak to Republican state lawmakers later this morning. Blunt then was expected to appear at a 12:30 p.m. news conference at the state Capitol with House Speaker Ron Richard, R-Joplin.
Bond had announced his Senate retirement at the state Capitol, first in a speech to the House chamber, then in a news conference in the same House Lounge where Blunt plans to speak.