Credit: Gage Skidmore / / CC BY SACredit: Gage Skidmore / / CC BY SAThe official Republican response to President Obama’s State of the Union address last night was from Florida Sen. Marco Rubio. But the Republican Party is a house (partially) divided now, with a self-conscious rebel wing, and the semi-official “Tea Party” response came from Kentucky Sen. Rand Paul. As Brian Doherty observes, Paul’s speech not only revealed key differences between his approach and that of Rubio, it showed that Paul’s brand of libertarianism has a central role to play in the future of the GOP, including the 2016 presidential campaign.