Update: A commenter asked why I’m surprised that two establishmentarians like McConnell and Cornyn would vote this way. Because, quite simply, I expected them to pander to tea partiers by voting with Cruz, secure in the knowledge that other Republicans who don’t have to face reelection next year like Coburn, McCain, Collins, Kirk, etc, would vote with Reid to defeat the filibuster anyway. McConnell could have had his cake and eaten it too. Instead he’s anti-filibuster. Odd.
They don’t want Cruz leading a filibuster against Obamacare.
They remember what happened when a similar filibuster over drones and killing American citizens made Rand Paul into a national hero among conservatives and some liberals.
They can read the polls, (and ignore cooked polls like the recent hack job from PMSNBC), and they’re afraid that Cruz will emerge from a filibuster, even if he loses, as a much bigger and more popular threat to them than he already is today.
What really worries the GOP establishment is that Ted Cruz just might lock up both the grassroots and the 2016 nomination early enough that he can’t be stopped, no matter how hard they try to derail him.