Longtime Chicago Mayor Richard Daley made the surprise announcement Tuesday that he will not run for re-election, in move that’s sure to set off a political scramble to fill the seat he’s held for more than two decades.

“Simply put, it’s time,” said Daley at a City Hall press conference. “It’s time for me, it’s time for Chicago, to move on.”

The 68-year-old Democrat has been Chicago’s mayor since 1989. He called the announcement “a personal decision, no more, no less” and said he and his family now begin “new phase of our lives.”

Daley made the announcement surrounded by family, including his wife, Maggie, who’s been battling cancer since 2002.

But the Mayor wouldn’t say whether his wife’s illness drove his decision not to run again.

“In the coming days I know there will be some reflecting on my time as mayor, many of you will search to find what’s behind my decision,” Daley said. “It’s simple: I’ve always believed that every person, especially public officials, must understand when it’s time to move on. For me that time is now.”

Chicago politicos have speculated for months as to Daley’s political future, and his announcement Tuesday is sure to set off a scramble to fill the executive power vacuum at City Hall. The February 2011 municipal race will be the first since 1947 when a sitting mayor will not run for re-election.

The announcement leaves an open door for White House chief of staff Rahm Emanuel, who said in an April television interview that he’d like to run for mayor of Chicago someday. He later dialed back those comments, but in a statement issued by his office shortly after Daley’s announcement, Emanuel didn’t rule out a mayoral run.

“While Mayor Daley surprised me today with his decision to not run for reelection, I have never been surprised by his leadership, dedication and tireless work on behalf of the city and the people of Chicago,” Emanuel said in the e-mailed statement.

Other possible names are Democratic Congressmen Jesse Jackson Jr. and Luis Gutierrez, and Chicago Ald. Bob Fioretti, among several others.

Alderman Joe Moore, 49th, has often been a critic of Daley administration policies, but said the disagreements have never been personal.

“There have been policy disagreements from time to time, but I’ve always had an amazing amount of respect for the Mayor and do not question at all his love for the city,” said Moore.

Mayor Daley left immediately after his announcement and did not take further questions.