These numbers seem inconsistent with Hypothesis One. How to explain them? We have a highly polarized politics that divides us along cultural lines. Those cultural divisions tend to be more important to voters than their ratings of presidents' and parties' performance. The polarization is exacerbated by the fact that Bill Clinton and George W. Bush both happen to have personal characteristics -- I don't have to spell them out, do I? -- that people on the other side of the cultural divide absolutely loathe.
The slight uptick in Republican percentages in 2002 and 2004 can be explained by higher Republican turnout. Looking ahead to next November, there is reason to believe that the Republican base is turned off -- by high spending, by immigration -- and may not turn out as heavily. But if so, how much difference will that make?
Polls are not good predictors of turnout -- only elections are. Last week, we had a special election in the 50th district of California, whose Republican congressman resigned in disgrace and went to prison. In 2004, the 50th district voted 55 percent for George W. Bush and 44 percent for John Kerry. Last week, the district voted 53 percent for Republicans (there were 14 candidates, the winner among whom goes on to a June 6 runoff) and 45 percent for Democrats. There were only two of them, and the leader, Francine Busby, got 44 percent of the vote -- the same percentage as Kerry. That may be 1 percent higher when the last absentees are counted.
These results are inconsistent with Hypothesis One. They're consistent with Hypothesis Two. Republican turnout was down more than Democratic turnout, but only very slightly. Of course, things may change by November. But it looks like Hypothesis Two is still in force, and if so, Democrats will have a hard time winning control of the House.