There you have it: Senate Democrats just prevailed 51-48
a vote to extend the Bush tax cuts only for incomes up to $250,000.
Vice President Joe Biden presided over the Senate. Sens. Joe Lieberman (I-CT) and Jim Webb (D-VA) voted with Republicans against the legislation.
Keep in mind, Harry Reid was unable to pull this off with larger majorities in 2009 and 2010.
Lots has changed since then, and no one factor contributed to the shift. Having President Obama on the ticket played no small role. That his opponent is Mitt Romney certainly made a difference. The White House's shift into a more aggressive, populist mode after last summer's debt limit debacle was a necessary ingredient.
Historians will have the benefit of hindsight to decide if this was part of a larger, post-financial-crisis shift in American politics that manifested itself in the Occupy Wall Street movement and continues to be fed by the anemic economy. Again, no one of these factors is dispositive and it's difficult to assign relative impacts to each one. But all of a piece.