(CNN) - National Republican Senatorial Committee Chairman John Cornyn said Thursday he expects fellow Texas Sen. Kay Bailey Hutchison will resign her seat "this fall sometime" to focus on a run for governor, according to the Houston Chronicle.
That would set up a special election in the spring of 2010 that could prove to be a headache for Republicans as they struggle to keep Democrats from getting a filibuster-proof 60 votes in the Senate.
"We certainly can't afford to lose that [Hutchison] seat," he said.
Hutchison has yet to formally announce she will challenge Gov. Rick Perry for the GOP gubernatorial nomination. But the third-term senator announced an exploratory committee in December, and already has a Web site and staff in place, ready for a primary campaign.
Several Texas Democrats are already gearing up for a hypothetical special election to replace Hutchinson. That list includes Houston Mayor Bill White, who has raised more than $2 million for the race.