How to Explain the Gambit by Senate Republicans?

I may have to stop blogging about politics altogether because I am simply unable to understand the political logic behind the Republican ultimatum on the Bush tax cuts.

Senate Republicans have announced their intention of holding hostage several important pieces of legislation - including the START treaty, extension of unemployment benefits, and a new budget (not to mention "Don't Ask, Don't Tell") - unless and until President Obama and the Democrats capitulate on extending the Bush tax cuts for the richest two-percent of Americans (see here). Regardless of the substantive merits of such an extension, I just don't get the politics.

On what political theory (or game theory) would a majority of the electorate support either the threat or its consequences, if the Democrats do not capitulate? Are the Republicans simply repeating the mistakes they made following the 1994 midterm elections, when they took over both houses of Congress and shut down the government in the mistaken belief that the public would blame President Clinton? Or is there some brilliant new political or game theory behind the current strategy with which I am unfamiliar?