WASHINGTON - A former chief of staff to Rep. Michele Bachmann (R-Minn.) wrote Tuesday that his former boss is "decidedly" not ready to be president.

"She is a faithful conservative with great oratory skills, but without any leadership experience or real results from her years in office," wrote Ron Carey in an op-ed published in the Des Moines Register, Iowa's leading newspaper. "She is not prepared to assume the White House in 2013," he concluded.

Bachmann officially launched her run for the presidency in Iowa Monday.

Carey, who worked for Bachmann from February to July 2010, said that during his time on her staff, her campaign and congressional offices were "wildly out of control."

"Stacks upon stacks of unopened contributions filled the campaign office while thousands of communications from citizens waited for an answer. If she is unable, or unwilling, to handle the basic duties of a campaign or congressional office, how could she possibly manage the magnitude of the presidency?" Carey wrote.

Carey also served as chairman of the Minnesota Republican Party from 2005 to 2009, and said his experience with the state's former governor, Tim Pawlenty, convinced him that Pawlenty, who is also running for president, "possesses the judgment, the demeanor, and the readiness to serve as president."