PRINCETON, NJ -- An average of 42% of Americans currently identify as Democrats or say they are independent but lean to the Democratic Party. Slightly fewer, 40%, are Republicans or Republican leaners. That narrow two-percentage-point Democratic edge is closer to what Gallup measured in the third quarter of strong Republican midterm years such as 1994, 2002, and 2010 than in the strong Democratic years of 1998 and 2006.
Gallup began to regularly measure Americans' party identification, including a follow-up question asking political independents whether they lean Democratic or Republican, in 1993. The combined measure of initial party identification plus the political leanings of independents is useful because it more closely resembles the Republican or Democratic choice voters have in elections. Since 1993, Gallup has found considerable variation in Americans' party preferences during midterm election years. These differences, particularly in the third quarter, have provided a good indication of which party would fare better in that fall's midterm elections.
Over the last two decades, Democrats have typically enjoyed an advantage in partisanship among the U.S. adult population. However, Republicans usually vote at higher rates than Democrats. That Republican Party turnout advantage leaves the Democratic Party politically vulnerable in midterm election years when they do not have a significant cushion in partisanship.
In years when the Democrats had a narrow advantage in partisanship among all adults, the usual Republican turnout advantages have resulted in a voting electorate composed of more Republicans than Democrats. Such years include 1994, 2002, and 2010, when Republicans gained seats in the House of Representatives.
In years when Democrats enjoyed a wide lead in partisanship, even as Democrats turned out at lower rates than Republicans, the electorate still included more Democrats than Republicans. The two years that fit that description -- 1998 and 2006 -- are the years in which Democrats gained seats in the House. The Democrats also picked up Senate seats in 2006, but 1998 saw no net change in Republican vs. Democratic seats in the Senate.
While the third-quarter partisanship figures provide a broad indication of which party is likely to gain seats in a midterm election, they are less likely to shed light on how many seats a party will win. For example, Republicans gained far more seats in 1994 and 2010 than in 2002, although the partisanship gap was similar in all three years. And Democrats gained many more seats in 2006 than in 1998, with fairly similar Democratic edges in partisanship each year.
The number of seats gained may be determined more by structural factors such as the political makeup of the government and how the parties performed in the prior election. For example, Republicans may have gained more seats in the 1994 and 2010 elections because each followed two years in which a Democratic president and Democratic House and Senate governed the country, after strong Democratic election years in 1992 and 2008. Additionally, Presidents Bill Clinton and Barack Obama were relatively unpopular in 1994 and 2010, respectively, with approval ratings in the mid-40s.
The 2006 elections followed four years of unified Republican government after strong Republican showings in the 2002 and 2004 elections.
Although President Obama is currently unpopular, Republicans have the majority in the House of Representatives after making big gains in the 2010 elections, which were largely maintained in 2012. Thus, it is not clear how much larger the Republican majority could get after this year's elections. Republicans may be poised for more significant gains in the senate, especially because many of the Democratic incumbents defending their seats were elected in 2008, a very favorable political year for Democrats.
Democrats currently have a narrow advantage in terms of Americans' identification with the two major parties, but based on historical turnout and other structural patterns, this small advantage suggests that the Democrats face a tough election environment this year. As Gallup demonstrated earlier this summer, President Obama's below-average job approval rating and Americans' low level of satisfaction with the way things are going in the country are also ominous signs for the Democrats. Historically, these indicators are unlikely to change in a short period of time such as the three months between now and Election Day.
With Democrats' advantage in partisanship currently consistent with where it has been in previous strong GOP midterm election years, it is imperative that Democrats match or exceed Republican turnout this fall if they hope to keep control of the Senate and minimize the size of the Republican majority in the House.
Results for this Gallup poll are based on telephone interviews conducted July 1-30, 2014, on the Gallup Daily tracking survey, with a random sample of 14,713 adults, aged 18 and older, living in all 50 U.S. states and the District of Columbia.
For results based on the total sample of national adults, the margin of sampling error is ±1 percentage point at the 95% confidence level.
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 of national adults includes a minimum quota of 50% cellphone respondents and 50% landline respondents, with additional minimum quotas by time zone within region. Landline and cellular telephone numbers are selected using random-digit-dial methods. Landline respondents are chosen at random within each household on the basis of which member had the most recent birthday.
Samples are weighted to correct for unequal selection probability, nonresponse, and double coverage of landline and cell users in the two sampling frames. They are also weighted to match the national demographics of gender, age, race, Hispanic ethnicity, education, region, population density, and phone status (cellphone only/landline only/both, and cellphone mostly). Demographic weighting targets are based on the most recent Current Population Survey figures for the aged 18 and older U.S. population. Phone status targets are based on the most recent National Health Interview Survey. Population density targets are based on the most recent U.S. census. All reported margins of sampling error include the computed design effects for weighting.
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.
For more details on Gallup's polling methodology, visit www.gallup.com.