Updated

A congresswoman widely considered to be the GOP's strongest candidate to unseat Sen. Robert C. Byrd (search) in 2006 announced Monday she will not challenge the Senate's oldest member.

Rep. Shelley Moore Capito (search), daughter of former three-term Republican Gov. Arch A. Moore Jr., said she plans to seek a fourth term in the House of Representatives instead.

"I took a lot of time with this decision," Capito told the Charleston Daily Mail. "My best future right now is to ask voters to send me back to my seat in Congress. I feel I've been very effective there, and there's more to be done."

Byrd announced last week he would seek a record ninth term in the Senate. The Democrat, who turns 88 in November and will become the longest-serving senator in U.S. history in June, said he was "ready to go another round."

The Republican Party has made unseating Byrd a top priority. The National Republican Senatorial Committee has already aired television ads questioning whether he remains in step with voters.

At least four Republicans have filed or announced plans to run for Byrd's seat, but national GOP officials had pinned their hopes Capito.