Bachmann, a prominent conservative lawmaker with ties to the grassroots Tea Party movement, said she would only support Boehner as the next Speaker if he were the only candidate available.
"Right now, we don't know exactly who the candidates will be. It may be John Boehner," Bachmann said in a debate on Minnesota Public Radio. "If John Boehner's the only candidate running, I'll be voting for John Boehner.
"I would look at all the candidates and weigh it accordingly," she added.
Some Republicans have been reluctant so far to commit to voting for Boehner as Speaker, should the GOP win back control of the House on Nov. 2. But defections and noncommittal statements have been largely limited to congressional candidates, and not incumbents like Bachmann, who is seeking her third term.
The Minnesota lawmaker's comments speak to the occasional worries conservatives have expressed about Boehner, and whether he'd adequately represent their views as the GOP's House leader.
Boehner sought to quell those worries in appearances in conservative media this week. "This is not a time for compromise, and I can tell you that we will not compromise on our principles," Boehner told conservative talker Sean Hannity on Wednesday.
It's not clear whether Boehner would face a viable challenger to his leadership if Republicans pick up the net 39 or more seats they need to reclaim the House majority. House Minority Whip Eric Cantor (R-Va.), Boehner's No. 2, has pledged support for the Ohio Republican.
Sergio Gor, a spokesman for Bachmann, said Thursday evening that the congresswoman supports Boehner.
"Congresswoman Michele Bachmann has been clear in her support for John Boehner. The Congresswoman stated earlier today that as far as she knows John Boehner is the only one running for Speaker, and won't speculate on other candidates," he said.
Updated 6:49 p.m.