South Dakota Sen. John Thune took a veiled swipe at Mitt Romney on the Senate floor Tuesday, saying it’s “easy” and “possibly even politically expedient to stand on the sidelines and criticize” the tax cut proposal backed by President Obama and GOP congressional leaders. “Inaction is not an option, and advocating against this proposal is no different than advocating for higher taxes,” Thune said in a Tuesday afternoon speech. Thune voted to advance the proposal in the Senate on Monday. Just a handful of Republicans, including possible 2012 candidate Jim DeMint (R-S.C.), opposed it. Thune did not mention Romney by...