CHICAGO – A day after snagging former Republican House Speaker Dennis Hastert’s congressional seat in a special election, Democrat Bill Foster knew Sunday he didn’t have much time to savor the victory.

Foster’s weekend win to fill the remainder of Hastert’s term until January will be a fleeting one for Democrats unless he can hold on to the seat in the fall election for a new, full term.

“The best way to establish a long-term career in Congress is to do a good job from Day One,” Foster told The Associated Press in a telephone interview while en route to a restaurant to thank voters.

A millionaire physicist and businessman, Foster defeated wealthy Republican Jim Oberweis after a contentious campaign with 53 percent of the nearly 100,000 votes cast in the special election Saturday.

The longest-serving Republican speaker in history, Hastert resigned the seat late last year after losing his powerful speaker post when Democrats took control of Congress in the 2006 election. He spent two decades in Washington.

Foster won a Democratic primary by less than 400 votes to be the candidate in the November race, although one challenger has initiated a re-count.