The last two elections have seen the fewest incumbents defeated by challengers in all of American history - four in 2002 and five in 2004. In 2004, the average margin of victory for House incumbents was 40 percentage points.

The result is a coordinated political apparatus skilled at designing and presenting even unpopular policies so that they don't set off alarm bells.

Consider a GOP tactic that has come to be called "catch and release." After the leadership has assured itself that a controversial bill will pass, moderate Republicans are released to cast highly publicized votes of "conscience." This is one reason why so many big bills end up magically squeaking through with no votes to spare.