After weeks of speculation about his timetable, former Speaker Dennis Hastert (R-Ill.) formally ended his 21-year Congressional career Monday night.

But it remains unclear when a special election to replace him will be held.

In a letter submitted to Illinois Gov. Rod Blagojevich (D) on Monday night, Hastert wrote, “I have chosen this date [to resign] because I have been advised that it allows you sufficient time to call a special primary to select candidates to run to fulfill my unexpired term on February 5, 2008, an already established primary day. This will minimize inconvenience to the voters and expense to the counties in the 14th Congressional District.”

Under state law, Blagojevich has five days to schedule a special election to fill Hastert’s vacancy. Assuming the special primary is held on Feb. 5, a special general election would have to be held by late March.

The candidates who already were running to replace Hastert — who announced his retirement plans in August but only recently disclosed that he would not serve out the remainder of his term — have not said whether they will compete in a special election, but most, presumably would.

Although Hastert held the suburban Chicago district with ease, the race to replace him is expected to be competitive between the parties. The leading Republican candidates are state Sen. Chris Lauzen and dairy magnate Jim Oberweis. On the Democratic side, scientist Bill Foster is the frontrunner for the nomination.

— Josh Kurtz