That said, the false equivalence drawn between Republican partisanship and Democratic partisanship is annoying.
Second, in a gesture of political hostility and brinkmanship, the Republicans, as a unified whole, refuse to raise the debt ceiling. This almost brings the nations finances crashing to a halt. Dems finally cave, so as to not plunge the nation into economic crisis, and sign some fairly ugly spending cuts into law. As a result of this stupid gesture of intransigence on the part of Repubs, the rating agency Standard & Poors downgrades the U.S. credit rating, for the first time in history, citing "political brinkmanship" as the problem. Repubs are willing to hold the nation hostage to get what they want. Dems have not yet resorted to such extreme, coercive methods.
Third, despite the hostility and unwillingness to play fair on the part of Repubs, Dems are still willing to help the "Just Say No Republicans" pass legislation for the good of the country. Recently, Obama and the Dems got behind a Republican proposal to make it easier for small businesses to obtain financing and investment. Dems are still willing to listen to Republican ideas.
Finally, political scientists can actually chart the Republicans swift shift to the hard right. This same study shows that Dems haven't moved very much, or at least their not doing so at a rate nearly as fast as Republicans. Therefore, the empirical evidence suggests that the gridlock in Congress is a Republican shift, not a Democratic one.