Just two years ago, in the giddy aftermath of Mr Obama's historic victory, Washington DC pundits were writing obituaries for the modern Republican party.

Now Republicans are back at the table, and what's more, they're holding most of the cards. There are several possibilities for how they'll play them.

The first - and most widely expected - scenario is for Washington DC to return to a state of absolute, fiercely partisan gridlock, a replay of the conflict ushered in by the Republican takeover of Congress in 1994, when Newt Gingrich became speaker of the House and ultimately shut down the government.

With control of the House, Republicans can block any legislation the White House pushes. Although they will not have the numbers to pass any of their own bills through the Senate alone, they can easily cause a stalemate.

Republicans who want to see Mr Obama hamstrung and struggling heading into 2012's presidential election see this as the best option.

"The single most important thing we want to achieve is for President Obama to be a one-term president," Senate Minority Leader Mitch McConnell said in an October interview, widely interpreted as a signal that he wanted the president's legislative agenda to stall. Continued...