Democrats are taking renewed interest in a congressional district where an eight-term Republican incumbent won by a little more than 1,000 votes last year.
Rep. Deborah Pryce, 56, has scheduled a news conference Thursday in Columbus, where she's expected to announce that she will retire when her term ends next year.
Pryce, who last year faced the toughest race of her congressional career, rose to the No. 4 position in the GOP before it lost control in the 2006 election.
Top Republican officials in Ohio and Washington said Wednesday that Pryce would not seek re-election. They spoke on condition of anonymity because Pryce had not made the announcement.
One of the officials said the decision was largely a family matter for Pryce, the single parent of an adopted child.
She defeated Democrat Mary Jo Kilroy in an election so close it required a recount. Kilroy, a Franklin County commissioner, plans to run for the seat in 2008, an election in which Democratic hopes run high because of voter disenchantment with President Bush and the Iraq war.
Pryce's decision means that of the four top House Republicans from that party's last majority, only Roy Blunt of Missouri, the GOP whip, will seek election next year.
Former Speaker Dennis Hastert planned to announce Friday that he would not seek re-election next year, party officials said, and in May, Rep. Ray LaHood said he was retiring after next year. Both are from Illinois. Former Majority Leader Tom DeLay, R-Texas, stepped down last year.
Even before Pryce's plans became known, Democrats saw her Columbus-based district as among the most competitive held by a Republican. An open seat will be even more difficult for Republicans to defend, but party activists say they will do so, arguing that Democrats already failed once - in 2006 - when many factors were in their favor.
Doug Thornell, a spokesman for the Democratic Congressional Campaign Committee, said: "Mary Jo Kilroy came within 1,055 votes of winning last cycle, and we expect this race to provide us with a tremendous opportunity to strengthen our majority."