CHICAGO — Former White House chief of staff Bill Daley officially stepped into the 2014 Illinois governor's race Tuesday by filing paperwork with state election officials, making him the only announced Democratic challenger to Gov. Pat Quinn.

More than a month after Daley released a videotaped announcement that he'd formed an exploratory committee, Daley filed the paperwork hours after releasing another video late Monday in which he said "there is no exploratory piece of this anymore."

Daley has been acting like a candidate in recent weeks, holding press conferences in which he has blasted Quinn for his handling of the state's pension crisis and other issues. In the latest video, that was his theme again, saying that the fact that the state Legislature adjourned in May without finding a solution on state pensions or vote on same-sex marriage represents a "dysfunction." He's also taken statewide campaign tours.

"I think the biggest problem right now is the lack of leadership," he said in the 54-second video, during which he never mentioned Quinn by name.

Quinn, also a Chicago Democrat, hasn't spoken about his 2014 plans in detail aside from saying the best way to campaign is to continue doing his job as governor.

"Nobody's built more as governor of our state than I have," he told reporters Tuesday after an unrelated event in Chicago.

Daley's campaign spokesman Pete Giangreco said Daley filed paperwork on Tuesday with the Illinois Board of Elections to remove the exploratory committee label from his campaign.

Giangreco said that a number of factors prompted Daley to jump into the race. He said Daley was encouraged by his ability to raise about $800,000 in less than three weeks, as well as his reception by mayors and others in visits he made to 11 downstate counties.

"He went through all that and (concluded) it all added up to a vibrant, and viable candidacy," Giangreco said.

A number of Republicans have declared candidacy, including Chicago venture capitalist Bruce Rauner, Illinois Treasurer Dan Rutherford and state Sens. Bill Brady and Kirk Dillard, but Quinn and Daley are the only Democrats.

Earlier this month, Illinois Attorney General Lisa Madigan, who was widely considered Quinn's most serious challenger if she ran, announced that she had decided not to. In an emailed statement, she said she never planned on running if her father, longtime House Speaker Michael Madigan, remained in his job.

A member of Chicago's first political family, Daley's brother, Richard M. Daley, and father, Richard J. Daley, were each mayor for more than 20 years and are widely considered among the most powerful mayors in American history.

While Bill Daley, the youngest son of Richard J. Daley, has flirted with runs for political office, including governor of Illinois, he never has done so. He has appeared more comfortable in supporting roles, spending years as a Democratic operative. He also was tapped by President Bill Clinton in his first term to push through the North American Free Trade Agreement through Congress, and selected after Clinton's re-election to be secretary of commerce, a post he held from January 1997 to July 2000.

President Barack Obama chose him as his chief of staff to replace Rahm Emanuel after Emanuel stepped down to run for Chicago mayor when Daley's brother decided not to seek a seventh term.