As is usually the case, Elizabeth Drew helps explain the current political situation. (You may not feel any better after reading her, but at least you'll better understand the gridlock and partisan nastiness.)
In 2010, the Republicans were sufficiently worked up about the new health care law and an old standby, “government spending,” particularly the stimulus bill, to drive them to the polls in far larger numbers than the Democrats. A slight upward tick in turnout numbers can have a disproportionate impact in Congress and many of the states, and therefore the country as a whole. The difference in turnout caused such a change in 2010; in fact, the Republicans gained sixty-three House seats and took control of both the governorships and the legislatures in twelve states; the Democrats ended up with control of the fewest state legislative bodies since 1946. The midterms go a long way toward explaining the dismaying spectacle in Washington today. State elections bear much of the responsibility for the near paralysis in Congress thus far this year and the extremism that has gripped the House Republicans and is oozing over into the Senate.
And here's the big takeaway:
Little wonder, then, that there can be such a gulf between the president and Congress, particularly the House of Representatives—but also between the president and the governments of most of the twenty-four states over which the Republicans now maintain complete control; almost half of these were elected in 2010. Democrats have complete control over fourteen states. The Republican-controlled states include almost all the most populous ones outside of New York and California. Since the midterms of 2010 the Republicans in most of these states have pursued coordinated, highly regressive economic policies and a harsh social agenda. Thus, while there’s largely been stalemate in Washington, sweeping social and economic changes that are entirely at odds with how the country voted in the last presidential election have been taking place in Republican-controlled states.
The New York Review of Books has the whole story, The Stranglehold on Our Politics