Voters Give Republicans an Edge in Senate Races, House Too Close to Call


Oct 16, 2014

U.S. Capitol in autumn

Photo by sborisov/Fotolia

In our continuing series, RAND is conducting surveys leading up to the midterm elections in November. In addition to asking people about their voting intentions, we're asking about their beliefs and opinions about some of the nation's most pressing issues.

Predicting Winners in the House and Senate

According to the new RAND American Life Panel (ALP) data, significantly more (five percent) respondents anticipate that Republicans will take the Senate for their state compared to those who anticipate that Democrats will, while there is not a clear difference in opinion regarding the race for the House.

Figure 1. Perceived Probability Party Will Win

Perceived Probability Party Will Win

We asked the following question of respondents:

There will be a general election in your state in November, including an election for the member of the U.S. House of Representatives from your district [and the U.S. Senator from your state], plus other state and local offices. [There will also be an additional special Senate election in your state to fill a vacated position.]

What do you think is the percent chance that each of the candidates will win in the election?

The percent chance can be thought of as the number of chances out of 100. You can use any number between 0 and 100. For example, numbers like 2 and 5 percent may be 'almost no chance,' 20 percent or so may mean 'not much chance,' a 45 or 55 percent chance may be a 'pretty even chance,' 80 percent or so may mean a 'very good chance,' and 95 or 98 percent chance may be 'almost certain.'

  Democrat Republican Someone Else
House ____% ____% ____%
[Senate] ____% ____% ____%
[Senate (Special)] ____% ____% ____%

We ask respondents about likely winners because previous research (PDF) has suggested that asking people who is likely to win an election is a better predictor of the results than asking who they will vote for. These results further confirm our findings from last week that the predicted results for the House of Representatives are too close to call.

The numbers presented above use results from a RAND ALP survey conducted from 12:01AM Sunday Oct. 5 to 11:59PM Oct. 11 and included 2,752 adult respondents.

Voter Turnout

Voter turnout during midterm elections is often less than 50 percent. While many get excited about presidential elections, House, Senate, and local elections garner less excitement. Furthermore, if potential voters expect the election to be a landslide, they may not be inclined to participate. We use responses from the question above about the expected outcome of the elections, respondent political party affiliation, and their self-reported probability of voting to assess who is likely to turnout on Election Day.

In what follows, we merge responses from the week of Oct. 5 with responses from the week of Sept. 29, when we measured the probability of voting and party affiliation. In this case, our analysis is limited to 2,374 adults who responded in both weeks. Survey weights are included to adjust for non-response. Additional details are available in our methodology report.

Figure 2 presents the mean reported probability of voting by whether respondents view their district leaning towards Democrats or Republicans and by the respondent's own party affiliation. The probability of voting is based on survey responses from our first survey and is detailed in our methodology report. We used responses from the question above, about whether the Democratic candidate or the Republican candidate will win the House election, to identify whether respondents believed they lived in a district that was Democratic-leaning (60 percent or more likely that a Democrat would win that district), Republican-leaning (60 percent or more likely that a Republican would win), or a divided district with no clear leaning (the rest) – giving roughly a third in each category. And we used respondents' self-reported political affiliation: Democrat or Republican, or Independent and Other.

Across all types of districts, Democrats are equally likely to vote. Republicans are significantly more inclined to vote in Republican-leaning districts than divided districts. Focusing on Republican-leaning districts only, Republicans are more likely to vote than Democrats.

Surprisingly, overall voter turnout is anticipated to be lowest in the divided districts; respondents in divided districts reported a voting probability of 65 percent, while respondents in Democratic-leaning districts reported a probability of 71.5 percent, and a probability of 79 percent in Republican-leaning districts. Each of these turnouts is significantly different from one another, suggesting that, contrary to the notion that people are more likely to vote when there is more of a chance their vote will make a difference, in general, people appear least likely to vote in this situation.

Figure 2. Probability of Voting, by District Lean and Political Affiliation

Probability of Voting, by District Lean and Political Affiliation

Katherine Carman is an economist and Michael Pollard is a sociologist at the nonprofit, nonpartisan RAND Corporation.