Rep. Michele Bachmann (R-Minn.) will endorse Mitt Romney’s presidential bid on Thursday, a campaign source confirmed.

A one-time front-runner in the GOP presidential race, Bachmann didn’t endorse any candidate after dropping out of the race in January following a 6th-place finish in Iowa’s caucuses. Most expected if she did endorse while the primary was still in full swing, it would be for Rick Santorum, who snagged her spokeswoman and many of her supporters after she bowed out.

Bachmann was a harsh critic of Romney during the GOP debates, persistently questioning his conservatism — particularly on social issues such as abortion.

But while Bachmann has remained coy about her endorsement plans since leaving the race, she has also softened her rhetoric on Romney, and insisted that she would be a force for GOP unity behind the party’s presidential nominee.