“Polarized Politics and the 2004 Congressional and Presidential Elections” by Gary C. Jacobson, in Political Science Quarterly (Summer 2005), 475 Riverside Dr., Ste. 1274, New York, N.Y. 10115–1274.

When the elections of 2004 were over, the Republicans stood triumphant, their lease on the White House extended and their holds on the House and Senate strengthened. Though denied a ringing national endorsement from the polarized electorate, they enjoyed something more useful for victory: a big “structural” advantage.

The Republicans’ continued control of the House was never in doubt, says Jacobson, a political scientist at the University of California, San Diego. “The reason is simple: Republican voters are distributed more efficiently across House districts than are Dem­ocratic voters.”

This structural edge can be seen by looking at how Democrat Al Gore’s roughly 540,000-vote advantage in the national popular vote in 2000 dissipates when the votes are tallied by congressional district: In only 195 districts (as currently configured) does Gore outpoll George W. Bush; in 240 districts Bush does better than Gore.

Gerrymandering by Republicans in Florida, Ohio, Texas, and other states after the 2000 census is partly responsible for their structural advantage in the House. They picked up 15 seats through redistricting, while losing only six elsewhere. (Democrats’ small gains through gerrymandering in states where they controlled the process were offset by pro-GOP changes in states where neither party was fully in control.) The other reason for the GOP edge, says Jacobson, is that minority and urban voters, who disproportionately favor Democrats, “tend to be clustered in districts with lopsided Democratic majorities.”

The more efficient distribution of Republican voters was also the Democrats’ main problem in the 2004 Senate contests. Twenty-two of the 34 states with senatorial elections were states that Bush had carried four years earlier. “Democrats had to defend 10 seats in states Bush had won . . . [while] Republicans were defending only three seats in states won by Gore.” The structural outlook for the Democrats in 2006 is not much more favorable, says Jacobson.

In both Senate and House elections in 2004, the long-term trend against ticket splitting continued. In 27 of the Senate contests, voters picked senate and presidential candidates from the same party—the highest level of such partisan consistency since 1964. Bush’s strenuous efforts as president and as candidate to cater to and mobilize his party’s base, alienating moderates and Democrats in the process, undoubtedly encouraged that trend, says Jacobson.

But the intense partisanship has a price: Postelection polls gave Bush the lowest overall approval ratings of any newly reelected president since Dwight Eisenhower in 1956. That’s a price Republican leaders are evidently willing to pay. With an evenly divided electorate and the GOP’s structural edge, they now have little electoral incentive to follow through on the pledge Bush made in 2000 to be “a uniter, not a divider.”