Bayer, R-Boise, is taking on Moyle, R-Star, who was elected House Majority Leader in 2006.
Bayer said his work on the budget committee has built good rapport with colleagues and that he's well suited to be part of the leadership team in a difficult 2011 legislative session.
"We're in a very challenging year, one of the toughest budget years ever," Bayer said Wednesday. "I believe I have things to offer in a leadership position, including professionalism and good relationships with the Senate and the governor's office."
Bayer has been quietly campaigning in the 57-member GOP caucus and made a number of campaign contributions to colleagues for the 2010 election. He also walked precincts for a half-dozen candidates.
Bayer phoned Moyle on Monday night to inform him of his challenge, the same day Senate President Pro Tem Bob Geddes, R-Soda Springs, said he would be stepping down after a decade as the Senate's top leader.
Moyle had toyed with the idea of challenging House Speaker Lawerence Denney, R-Midvale, but now says he'll defend his spot as the GOP's floor leader.
"You take every race seriously," Moyle said. "I won by 13 votes when I first ran for the Legislature."
Bayer was elected Nov. 2 to a fifth two-year term. He has been an influential member of the Joint Finance-Appropriations Committee and is a close ally of newly elected 1st District GOP Rep. Raul Labrador.
Moyle was elected to a seventh term.
At least one other House leadership race will be decided at the GOP closed-door caucus on Dec. 1: House Education Committee Chairman Bob Nonini of Coeur d'Alene is challenging Caucus Chairman Ken Roberts, R-Donnelly.
You can follow Idaho Statesman Politics on Twitter.