According to numerous reports, former Sen. Dan Coats (R., Ind.) will challenge Sen. Evan Bayh (D., Ind.) for the seat he previously held from 1989 to 1999. NBC’s Chuck Todd points out that this is a “delayed matchup from ‘98″ when “Coats chose retirement rather than face [an] uphill battle against then-Gov. Bayh.” Two Republicans, former Rep. John Hostettler and state Sen. Marlin Stutzman, are already in the race.

Coats was appointed to the seat in 1988 after Dan Quayle was elected vice president. He was re-elected in 1990 and 1992. Coats, now 66, also served in the House from 1981 to 1988. Since leaving the Senate, he has served as U.S. ambassador to Germany and (somewhat infamously) as shepherd for the failed nomination of Harriet Miers to the Supreme Court in 2005.

More from Marc Ambinder:

Coats was a key behind-the-scenes force in convincing John McCain to take Sarah Palin seriously as a vice presidential candidate. He was a member of “The Family,” a close-knit group of rigorously evangelical Christians who run, among things, the now well-known C Street rooming house in Washington, D.C. He also lobbied on behalf of Roache Diagnostics during the health battle reform battle. He currently is a “senior policy adviser” for the firm of King and Spalding. He has also been a registered lobbyist for Bank of America, Lockheed Martin and the Decision Sciences Corporation. . . . In the Senate, he served on the Armed Services and Intelligence Committees, among others. . . . Bayh has more than $12 million in the bank.

If he’s in, Coats will have to hustle (h/t Journal Gazette):

A senior Republican official said the announcement is not likely to be made until after the Super Bowl this weekend and that the national Republican Party has promised help in getting the necessary 4,500 signatures to make him eligible for the primary ballot. He would have less than three weeks to obtain 500 signatures in each of the state’s nine congressional districts.

Other sources say an announcement could come later today.