TALLAHASSEE — George Sheldon, who served as secretary for the Florida Department of Children and Families under Gov. Charlie Crist, said Monday he will seek the Democratic nomination to challenge Republican Attorney General Pam Bondi.

Sheldon, 66, resigned Friday from his $179,000 job as the U.S. Department of Health and Human Services' assistant secretary for the Administration for Children and Families. To catch up to Bondi's $1.2 million in campaign contributions, Sheldon said he started calling donors Saturday.

Sheldon's announcement comes ahead of this weekend's Democratic Party state conference in Orlando, giving him a head start on other contenders, which could include Florida House Minority Leader Perry Thurston of Fort Lauderdale. If Sheldon wins the nomination, the race would pit Bondi, the state's most vocal critic of the Affordable Care Act, against Sheldon, who is leaving the agency implementing it.

Sheldon said his campaign will emphasize integrity in the AG's office, which he said has slipped because of Bondi's re-election bid. He questions her decision to delay a September execution so she could host a fundraiser and a $25,000 contribution from Donald Trump after complaints were made about "get-rich-quick" seminars associated with him.

"(The delayed execution) raises serious questions about how she sees the position," Sheldon said. "(The Trump donation) sends the wrong message. … She should ask the committee to return the check."

Bondi campaign manager Pablo Diaz released a statement saying, "Pam Bondi has fought hard to defend and protect the people by making Florida a zero tolerance state for pill mills, taking on human trafficking, and pursuing consumer relief from both mortgage and Medicaid fraud. Pam Bondi and George Sheldon have very different credentials and points of view."

Sheldon's political career stretches back to 1969 when he was a legislative aide to then-state Sen. Reubin Askew. An attorney, Sheldon served as a Tampa state representative from 1974 to 1982. After losing a close U.S. congressional race in 1982 against Mike Bilirakis, Sheldon worked in private practice until 1999 when Florida Attorney General Bob Butterworth tapped him as a deputy AG. He also worked with Butterworth at DCF.

"He was an outstanding administrator," Butterworth said. "He helped turn DCF from the worst agency in state government to the best."

Sheldon could be at the top of next year's Democratic ticket with the man who has been both ally and nemesis — Crist.

In 2000, Crist beat Sheldon for education commissioner, but not before he ran a TV ad that highlighted Sheldon's 1984 DUI arrest. Crist pulled the ad, which aired three times.

After Butterworth stepped down as DCF secretary in 2008, Crist tapped Sheldon for the job. As their relationship evolved, the subject of the ad never came up.

"My arrest was a dumb mistake, so it was fair game," Sheldon said.

"I always regretted that," Crist said Monday. "I hope he forgave it. He's a dear friend, a brilliant lawyer and a dedicated public servant. I can't say enough good things about him."

Contact Michael Van Sickler at mvansickler@tampabay.com.