(CNN) - Fresh off her announcement she is running for governor, Texas Sen. Kay Bailey Hutchison said Wednesday she expects to resign her Senate seat sometime in the fall, a move that will set up a pivotal special election next spring.
"The actual leaving of the Senate will be sometime - October, November - that, in that time frame," the Republican senator told Texas radio station KBH.
She later told reporters the resignation could come more toward the end of the year so she can be present for pivotal votes on health care and energy legislation.
Current Texas Gov. Rick Perry, whom Hutchison is challenging for the GOP gubernatorial nomination, is expected to appoint a replacement until the special election is held a few months later.
The spring matchup - likely to be viewed as a prelude to the national midterm elections the following fall - could prove to be a headache for Republicans as they struggle to hold Democrats to the already filibuster-proof 60 votes in the Senate.
"We certainly can't afford to lose that [Hutchison] seat," National Republican Senatorial Committee Chairman John Cornyn said last May
Several Texas Democrats have already geared up for the special election, including the cash-flush mayor of Houston, Bill White. So far this year, White has reported raising more than $4 million for his bid.
- CNN's Ted Barrett contributed to this report