PRINCETON, NJ -- Republicans lead by 51% to 41% among registered voters in Gallup weekly tracking of 2010 congressional voting preferences. The 10-percentage-point lead is the GOP's largest so far this year and is its largest in Gallup's history of tracking the midterm generic ballot for Congress.

These results are based on aggregated data from registered voters surveyed Aug. 23-29 as part of Gallup Daily tracking. This marks the fifth week in a row in which Republicans have held an advantage over Democrats -- one that has ranged between 3 and 10 points.

The Republican leads of 6, 7, and 10 points this month are all higher than any previous midterm Republican advantage in Gallup's history of tracking the generic ballot, which dates to 1942. Prior to this year, the highest such gap was five points, measured in June 2002 and July 1994. Elections in both of these years resulted in significant Republican gains in House seats.

Large leads on the generic ballot are not unprecedented for Democrats. The widest generic ballot lead in Gallup's history was 32 points in the Democrats' favor, measured in July 1974, just prior to Republican President Richard Nixon's resignation over the Watergate scandal. This large margin illustrates Democrats' historic dominance over Republicans in registered voters' party identification in the decades since World War II. Democrats controlled the House of Representatives continually between 1955 and 1995, and routinely held generic ballot leads in the double digits during that period.

Republicans Have 25-Point Lead on Enthusiasm

Republicans are now twice as likely as Democrats to be "very" enthusiastic about voting, and now hold -- by one point -- the largest such advantage of the year.

Republicans usually turn out in higher numbers in midterm elections than do Democrats, and Gallup's likely voter modeling in the final weeks of an election typically reflects a larger GOP advantage than is evident among registered voters. The wide enthusiasm gaps in the GOP's favor so far this year certainly suggest that this scenario may well play itself out again this November.

Bottom Line

The last Gallup weekly generic ballot average before Labor Day underscores the fast-evolving conventional wisdom that the GOP is poised to make significant gains in this fall's midterm congressional elections. Gallup's generic ballot has historically proven an excellent predictor of the national vote for Congress, and the national vote in turn is an excellent predictor of House seats won and lost. Republicans' presumed turnout advantage, combined with their current 10-point registered-voter lead, suggests the potential for a major "wave" election in which the Republicans gain a large number of seats from the Democrats and in the process take back control of the House. One cautionary note: Democrats moved ahead in Gallup's generic ballot for several weeks earlier this summer, showing that change is possible between now and Election Day.