Hutchison, a Republican, plans to tell Republican women in a speech in Galveston on Saturday that she is stepping down in 2010 because there are too many important issues facing Congress for her to quit this fall as she had originally planned. Her campaign provided the prepared remarks to The Associated Press on Friday.
"I realize this will keep me in the Senate past the primary election," Hutchison's speech says. "These issues are too important to leave the fight to a newly appointed freshman senator who will be selected in the midst of a political storm."
In the speech, she makes it clear that she will leave the Senate after the primary regardless of whether she or Perry wins.
The senior Texas senator said she is needed in Washington to fight against Democratic proposals to limit carbon emissions and overhaul the health care system. She said the policy debates are too important to leave to an appointed newcomer who would fill out the remainder of her term, which expires in January 2013.
Hutchison previously said she would leave the Senate in October or November to focus on the primary contest between her and Perry, the longest-serving governor in Texas history.
"We appreciate that Sen. Hutchison has taken the governor's advice and finally decided to make a decision to stay in Washington," Perry spokesman Mark Miner said in an e-mailed statement. "Hopefully this will allow her to be a full-time senator for the people of Texas."
A few of Hutchison's GOP colleagues in the Senate also chimed in on her decision.
"Throughout her career, Sen. Hutchison has always put her state of Texas first," said Sen. Mitch McConnell of Kentucky. "I applaud the decision Kay has made and am proud to have her standing with me in the U.S. Senate in our fight against more spending, more debt, higher premiums, higher taxes and cutting seniors' Medicare in the Democrats' health care plan."
"It is the right thing for Texas and America," said former Sen. Phil Gramm. "Having worked with Kay, I am confident that she can both protect us in Washington and run successfully for governor.”
Candidates from both parties have been lining up to run for Hutchison's seat without knowing precisely when she might step aside. Hutchison still isn't saying when it will be, but the 16-year Senate veteran will firmly state that she is going to give up the seat in 2010.
"I will be resigning this Senate seat," Hutchison says in the speech. "For all of the good Republicans out there who plan on running for my Senate seat next year, make no mistake, this is going to happen."
Omar Villafranca contributed to this report.