Cook County (Ill.) Sheriff Tom Dart announced Wednesday he will not run for mayor of Chicago, becoming the fourth high-profile politician to decline to run. 

All four announcements stand to benefit President Obama's former Chief of Staff Rahm Emanuel, who left the White House earlier this month to seek the office of mayor, which is being vacated by six-term Mayor Richard Daley (D).

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The sheriff said he could not balance running for mayor and raising his family, saying, "I just couldn't do both."

Dart's decision comes after Reps. Luis GutierrezLuis Vicente GutierrezIllinois Democrats propose new 'maximized' congressional map Biden's inauguration marked by conflict of hope and fear The Hill's Campaign Report: Democratic primary fight shifts to South Carolina, Nevada MORE (D-Ill.), Mike Quigley (D-Ill.) and Jesse Jackson Jr. (D-Ill.) all chose to stay out of the race. The announcements are a sign the field is clearing for Emanuel to become the front-runner in the race. 

The sheriff was thought to be Emanuel's top rival for the job. He is a former state representative from the South Side and has strong ties to the city's Democratic political machine. He gave clear signs he would enter the race, hiring Democratic consultant Joe Trippi as an adviser.

After Emanuel left the White House, some had questioned how successful his mayoral candidacy would be at connecting with Chicago voters, considering the seven-plus years he spent in Washington serving in Congress and the White House.

But Emanuel entered the race with federal campaign funds of more than $1 million and quickly hit the ground to campaign in the Windy City. Emanuel has already demonstrated how that large chunk of money could be used in the campaign: The Chicago Tribune reported that the former chief of staff bought $10,000 in voter records.

Other potential candidates have until Nov. 22 to file to enter the election, which will be held in Feb. 2011. The other two candidates who have officially announced are former Chicago school board chief Gery Chico and city clerk Miguel Del Valle.