PRINCETON, NJ -- Gallup tracking of 2010 congressional voting preferences shows Republicans moving back ahead of Democrats, 49% to 43%, by two points their largest lead of the campaign to date. Registered voters' preferences had been closely divided for the last several weeks.
These results are based on Gallup Daily tracking interviews conducted May 24-30. Republicans' largest advantage on the generic ballot prior to now was four points during the week of April 5-11. The GOP held a three-point advantage the week of April 12-18.
The shift from a more competitive race to a Republican lead occurred the same week President Barack Obama averaged a 46% job approval rating, his lowest weekly average to date.
Two structural changes in the data help explain the shift. First, while the percentage of registered voters identifying as Republicans has been consistent over the past several weeks, during the last week there was a decline in the percentage of voters identifying as Democrats and an increase in independent identifiers.
That is consistent with the type of movement in party identification Gallup has observed in recent months: a narrowing of the party gap caused mostly by movement away from the Democratic Party, with no appreciable gain in the percentage of Republican identifiers.
Second, while the preferences of Republican and Democratic registered voters have largely been stable in recent weeks, the now-larger group of independent registered voters has shifted more toward Republicans in its voting preferences.
Enthusiasm Holding Steady
Unlike the last time Republicans moved ahead of Democrats (in late March and early April), the current shift in voter preferences has not been accompanied by a change in reported voter enthusiasm. In fact, the 29% of registered voters who say they are "very enthusiastic" about voting in the midterm elections is the lowest Gallup has measured to date, continuing to show a drop from the brief surge in late March and early April, near the time of healthcare reform passage.
Still, Republicans continue to enjoy a healthy advantage in reported enthusiasm over Democrats -- 39% to 24% in the latest update. For the last four weeks, Democrats' voting enthusiasm has been at or below that of independents.
Given the Republican Party's usual advantage in voter turnout in midterm elections, a tie on the generic congressional ballot among registered voters, as Gallup has been reporting, typically suggests that the party would win the national popular vote for Congress if the election were held today. Now, with a lead on the generic ballot, Republicans could be in a slightly stronger position than they have been in, though it is not clear whether the recent shift marks the beginning of a lasting change in the structure of the race or perhaps a short-term response to political events such as the Obama administration's handling of the BP oil spill. The latter appeared to be the case earlier this year as Republicans built a small lead after the healthcare bill's passage into law, but the slight bump for the GOP among registered voters did not last.
Explore more Gallup data relating to the upcoming congressional midterm elections, including Gallup's complete generic ballot trend since 1950 in our Election 2010 key indicators interactive.
Results are based on telephone interviews conducted May 24-30, 2010, with a random sample of 1,594 registered voters, aged 18 and older, living in all 50 U.S. states and the District of Columbia, selected using a random-digit-dial sampling technique.
For results based on the total sample of national adults, one can say with 95% confidence that the maximum margin of error is ±3 percentage points.
Interviews are conducted with respondents on landline telephones and cellular phones, with interviews conducted in Spanish for respondents who are primarily Spanish-speaking. Each sample includes a minimum quota of 150 cell phone respondents and 850 landline respondents, with additional minimum quotas among landline respondents for gender within region. Landline respondents are chosen at random within each household on the basis of which member had the most recent birthday.
Samples are weighted on the basis of gender, age, race, Hispanic ethnicity, education, region, adults in the household, cell phone only status, cell phone mostly status and phone lines. Demographic weighting targets are based on the March 2009 Current Population Survey figures for the aged 18 and older non-institutionalized population living in U.S. telephone households. All reported margins of sampling error include the computed design effects for weighting and sample design.
In addition to sampling error, question wording and practical difficulties in conducting surveys can introduce error or bias into the findings of public opinion polls.