SPRINGFIELD - A top lieutenant of Illinois Senate President Emil Jones will seek the congressional seat being vacated by embattled U.S. Rep. Jerry Weller.

After a whirlwind weekend of meetings with top Democrats in the nation's capital, state Sen. Debbie Halvorson, D-Crete, said Tuesday she's entering the race for the 11th Congressional District seat.

"The place I can make the biggest difference is going to be in Washington DC," Halvorson told reporters Tuesday.

Halvorson, 49, is the Senate majority leader and is in line to someday potentially replace Jones as the top Democrat in the chamber.

Jones endorsed her candidacy Tuesday by saying she'd be missed in the Senate.

"It would be a tremendous loss, but she'll be a tremendous congresswoman," said Jones.

Halvorson is in the middle of a four-year term, which means she could run for the congressional seat and lose, yet still be able to return to her post in the state Senate.

"Losing is not an option. I don't plan on losing," said Halvorson.

Weller announced last month he would not seek an eighth term representing the district that runs from Chicago's south suburbs to Bloomington-Normal. He has been under fire for real estate dealings in Central America.

He said he is quitting to spend more time with his wife, a senator in Guatemala, and their young child.

Halvorson said she called Democrats who've shown interest in Weller's seat and has asked them to clear the field for her bid. She said she will have significant financial backing from the Democratic Congressional Campaign Committee.

"I have a tremendous amount of support coming my way," said Halvorson.

Potential GOP candidates include state Rep. Dan Brady of Bloomington and New Lenox Mayor Tim Balderman.

Jason Wallace, an Illinois State University student, plans to run as a Green Party candidate.

Brady said Tuesday he is still mulling his chances. He has spoken with GOP leaders in the counties that comprise the 11th district and is reviewing polling numbers.

He said Halvorson's entrance in the race would have no bearing on his final decision, which could come later this week.

But, Brady said, "Certainly, she would be a formidable candidate."

Unlike Halvorson, Brady's term ends in 2008, which means he will have to give up his seat representing the 88th district in the House if he runs.

Two Republicans have emerged as potential candidates for Brady's seat.

McLean County Republican Party Chairman John Parrott said he has spoken with both Scott Lay and Adam Kinzinger about running. Lay is a member of the Normal-based Unit 5 school board and Kinzinger is a former member of the McLean County board.

"They are waiting patiently," Parrott said.

Parrott said he is hopeful one will not run for the seat in order to avoid a divisive GOP primary.

"I've said I don't think a primary would be in their best interest," Parrott said Tuesday.