Historically, low presidential approval ratings and waning support among independent swing voters before a midterm election spell disaster for the president’s party. According to James Campbell, professor of political science at the State University of New York at Buffalo, the president’s party, on average, wins about 1.3 seats in the House of Representatives for every point of presidential approval. Bush’s current approval rating is higher only than that of Harry Truman, who lost 55 House seats in 1946; Ronald Reagan, who lost 27 House seats in 1982; and Bill Clinton, who lost 54 House seats in 1994.

Sixth-year midterm elections — that is, congressional elections held in a president’s second term — also are infamous for eroding the ranks of presidential allies in Congress. According to Larry Sabato, director of the University of Virginia’s Center for Politics, second-term presidents after World War II have lost an average of six Senate seats in their sixth years.

There have been signs recently that some Republicans in Congress are taking a cue from the past and distancing themselves from Bush. The Bush-backed U.S.-Central America Free Trade Agreement passed by only two votes in the House largely because of local opposition to the treaty in Republican-held congressional districts in the South. Senate Majority Leader Bill Frist broke with the president and reversed his earlier position on federal funding for stem cell research. Bush had to settle for a recess appointment of John Bolton because an unusually hostile Senate held up the weapons control expert’s nomination as ambassador to the United Nations. And the president’s high-profile Social Security plan has stalled in Congress for months.

But, notes Barry Burden, an assistant professor at Harvard who teaches the politics of Congress, “the last two midterm elections have not followed the historical trend.” From the Civil War to 1994, only once did a president’s party add congressional seats in a midterm election. In 1998, however, Clinton gained seats in the House, and Bush won seats in both chambers in 2002.

Congressional seats are generally safer than they used to be. According to Campbell, “The number of seats that could change, that are really in contention, … [has] declined substantially in the last quarter century” because incumbents now outspend challengers by 10 or 12 times, limiting the potential for large swings in the balance of power.

He adds, “There are fewer split-result districts than there have been for many decades,” meaning a greater number of congressional Republicans win in districts that voted for the Republican presidential candidate now than in the past. Disapproval of the president is generally concentrated in Democratic districts.

A structural oddity of congressional elections — what scholars refer to as the “geographic spatial advantage” of the GOP — also encourages Republican candidates to ignore the disapproval of independents and actively associate themselves with the president’s agenda.

“Democrats are overly concentrated in New York, Chicago and California,” Blendon says. “When you win a Democratic [congressional] district, you [might] win by 65 to 68 percent. The Republicans have more districts, which they [might] win by 55 or 57 percent. Which means [more] of the 435 districts … have a Republican majority by a smaller margin than their share of the president’s approval rating would suggest.”

“In 2000, Gore [won] by half a million votes out of 105 million cast,” Jacobson explains. If “you redistribute those votes into the current congressional districts, you get 240 districts where Bush outpolled Gore and only 195 districts where Gore outpolled Bush. So Democrats have more of their support wasted in districts which are overwhelmingly Democratic. Republicans are spread around more evenly.” There are also more solidly red states than solidly blue ones, giving most Republicans a similar electoral advantage in the Senate.

So as long as consistently Republican voters come out to vote in 2006, this skewed districting means that Democrats should not expect dramatic gains in Congress or more cooperation from the other side of the aisle in 2006 — even with Bush’s approval rating hovering in the mid to low 40s.

“If there were signs that Republicans were becoming disenchanted with Bush, that would really be interesting” because they might not turn out to vote, Jacobson says. “But I don’t see much sign of that.”

“What [Bush is] worried about is turning out Republicans, and if he can do that, they have more districts,” Blendon says. “His whole focus isn’t the normal focus — which is, ‘It’s independents, stupid’ — in the off-year election. His focus is motivating the base of his own party to turn out in their Republican-oriented districts.”

The advantage to Republicans of playing base politics — the so far successful GOP electoral strategy of emphasizing hot-button issues such as judicial nominations, restrictions on abortion, support for the war and teaching intelligent design in public schools to motivate conservative voters in districts with small Republican majorities — may keep most Republicans in Congress loyal to President Bush, even those facing imminent elections.

“The Republicans see themselves as needing terrorism, national defense, low taxes and the president’s leadership on those issues to be reelected,” Blendon says.

Despite the unease among some Republicans in Congress over Social Security and stem cell research, wooing the party’s base is still a priority for GOP lawmakers. CAFTA’s passage in the House over the objections of a mobilized opposition to the lowering of trade barriers counts as a presidential victory. This summer, the Republican Congress has also been pliant in passing White House-backed legislation popular with elements of the party base, OK’ing Bush’s long-stalled energy bill, a massive transportation bill and a law protecting gun companies from criminal liability.

Bush has the added advantage of senators who are angling for the 2008 Republican presidential nomination. Sens. George Allen of Virginia and Sam Brownback of Kansas are both beginning campaigns to grab the conservative Christian vote in the primaries after Sen. Rick Santorum, R-Pa., announced he would not run for president. As for their GOP rivals, “the Chuck Hagels and John McCains of the world want to make sure they are in good with party activists, and at times that might mean cozying up to the president,” Burden says.

“At the moment,” Blendon says, “the president and Karl Rove and his other advisors have convinced the Republicans in Congress that this strategy is going to work for them. Stick to the Republican issues, turn out the base, stay with where you are on the conservative agenda, don’t worry about the approval rating, and you’ll still do very, very well.”

Will playing base politics continue to work for Republicans? “There is not a lot of history of this being successful,” Blendon says. “Usually … in these off-year races independents … are very important.

“The agenda has been very conservative, very partisan, and [independents may] do what they have done before, which is just switch sides on their vote.”

A case in point is last week’s special election in Ohio’s 2nd District, in which the Republican candidate won with only 52 percent of the vote. Bush won the 2nd District with 64 percent of the vote in 2004, and no Democratic House candidate has received more than 40 percent of the vote there in decades. Former House Speaker Newt Gingrich opined last week that the Ohio election “should serve as a wake-up call to Republicans … Clearly, there’s a pretty strong signal for Republicans thinking about 2006 that they need to do some very serious planning and not just assume that everything is going to be automatically OK.”

Turnout for the special election was less than half that of 2004.

What’s more, with the midterm election still 15 months away, the continued loyalty of GOP lawmakers to the president is not written in stone. “If [congressional Republicans] panic,” Blendon says, “and they really begin to wonder, ‘Won’t this be like other elections where independents will turn out?’” support for the president and his agenda may erode.

For now, though, Republicans in Congress “really, strategically, have convinced themselves that the president’s got it right, that they can turn out these very high proportions, and they don’t have to shift their agenda,” Blendon says. “They’re tied to his fortunes.”