Rep. Rahm Emanuel (Ill.) will officially step down from his Congressional seat on Friday.

Emanuel — a force in the Democratic Party who ascended to House leadership in just two terms and was last month named President-elect Barack Obama’s chief of staff — notified Chicago constituents of his resignation in a robocall on Monday.

Emanuel’s office today also released his resignation letter to Illinois Gov. Rod Blagojevich (D), which was dated Jan. 2.

“It has been a tremendous privilege to serve the people of the Fifth District over the past six years,” Emanuel wrote to Blagojevich, who also once represented the 5th district in Congress. “I am grateful for the opportunity to represent the hopes and dreams of a quintessentially American district.”

The governor has five days to schedule a special election for the safely Democratic 5th district seat after receiving Emanuel’s resignation. The election must take place within 115 days of the announcement.

But with Blagojevich embroiled in a legal battle over allegations that he tried to sell Obama’s Senate seat, and with as many as a dozen candidates running to replace Emanuel, the special election will heap more attention on the Illinois political scene.