Senator Ted Cruz is refusing to endorse his fellow Texas Republican in next week's primary in which a tea party candidate is trying to oust the Senate's second-ranking GOP leader.
Cruz declined to say whether he will vote for Sen. John Cornyn or challenger Steve Stockman.
Cruz continued criticizing GOP leaders Thursday and said he doesn't plan to endorse any incumbents or their challengers in this year's primaries. He did not rule out changing his mind later.
Several senior Republican senators face tea party challengers in primaries.
Cruz's comments were notable because he is a vice chairman of the GOP committee tasked with winning Senate elections.
Cruz is a tea party favorite who may run for president in 2016.
His comments came at a Washington breakfast sponsored by Politico.