The two GOP office-holders have been squaring off for months, but now both candidates have formally entered the race. The winner of the primary will face the Democratic nominee in November 2010.
Perry has long suggested that Hutchison might not run, but her action Monday puts her in contention with Perry. Hutchison said Texas needs a "serious leader" and that she's that person.
Hutchison has said she'll remain in the Senate while running for governor. Perry filed last week to seek an unprecedented third term.