Sen. John McCain (R-Ariz.) took to Twitter on Friday to say he has "serious concerns w/ some provisions" of the tax legislation unveiled by Senate Majority Leader Harry Reid (D-Nev.), but that he'll support it anyway. The bill, introduced Thursday, leaves President Obama's compromise largely unaltered but adds tax credits for alternative energy, energy-efficient homes and other "green" efforts. These provisions aim to soothe liberal Democrats who oppose the deal's extension of tax cuts for the wealthy.