Hastert initially planned to make an announcement Thursday, but has since scrapped that decision, according to one GOP aide. The former speaker, who announced his plans to retire over the summer, is still expected to leave the House some time in December, but the date of his departure - as well as his announcement - remains unclear.
Hastert has been expected to announce his early resignation from the House at some point during the fall, but his move, which Roll Call first reported, still has an uncertain affect on the race to replace him.
Republicans are already locked in a hard-fought primary. But Democratic Gov. Rod Blagojevich could fast-track that intramural contest in order to schedule the special on the same day as the state's Feb. 5 primary - when Illinois Sen. Barack Obama will be on the ballot in his bid for the Democratic presidential nomination.
That latter scenario would give congressional Democrats - which Blagojevich once was - a major advantage in the special election to pick up a predominantly Republican seat because Democratic turnout is expected to be heavy in support of Obama.