WATERLOO, Iowa — Michele Bachmann, a Minnesota congresswoman with deep tea party appeal, was ready Monday to officially plow into the Republican presidential primary with a conservative and often freewheeling message honed to the party's base.

Greeted in her native Iowa with a new poll predicting she'll be a force in the state that opens the GOP nomination contest, Bachmann hopes to reshape both the 2012 GOP field and how she's viewed in the eyes of voters. After the formal Iowa kickoff, she planned to shift her focus to New Hampshire and South Carolina, other states with cherished traditions of separating the viable contenders from the political also-rans.