In this autumn's elections, a tendency is in tension with a rarity. The party holding the presidency has lost House seats in 32 of the 34 off-year (nonpresidential) elections since the Civil War. So the Republicans' majority in a House divided 223-210 is in danger. But rarely do parties gain seats in four consecutive elections. Democrats gained in the last three. A SHIFT OF SIX SEATS would make Dick Gephardt speaker, but could make George W. Bush's re-election easier. He could blame Democratic control of Congress for all discontents. And if Democrats control both houses, re-electing Bush would satisfy the...