Former Utah governor Jon Huntsman's struggling run at the GOP presidential nomination is replacing its campaign manager.Susie Wiles, the campaign manager and lead Florida operative, is leaving the campaign and will be replaced by communications director Matt David.

Sources say the Huntsman campaign is entering a new phase and Wiles was "no longer a good fit." The candidate is making the announcement to campaign staff Thursday afternoon.

Huntsman started his campaign one month ago today but poor polling results show he has struggled to gain traction in the race.

Sources say going forward the former Utah Governor's campaign plans to be "tighter, faster, more aggressive" and to begin drawing more stark contrasts with the rest of the GOP field, "particularly Romney."

While aides say that though Huntsman, the Obama Administration's former Ambassador to China is "not a podium pounder," he will stick to the facts and also begin a new, stern "indictment of the president."

Fox News Senior Political Correspondent Carl Cameron and producer Faith Mangan contributed to this report.