Assessing Obama’s Coattails, Part II: A Presidential Mandate?

In an earlier post (see here) I tried to assess media claims that Obama’s election signified a “mandate” from voters for change. One way to measure that mandate is to estimate Obama’s “coattails”, that is, the degree to which members of Congress feel that their own election depended in part on voters who came to the polls to support Obama. In theory, the longer a president’s coattails, the more leverage he has in Congress and the greater the size of his mandate. Historically, presidential coattails have been quite short in the modern era, but based on the initial press reactions that claimed an electoral mandate for Obama, there was some reason to believe that his coattails might extend a good deal longer than those of his recent predecessors.

A simplistic way to assess a president’s coattails is to examine whether Obama received more votes than the winning Senate or congressional candidate in each of the 33 states and 435 congressional districts that held elections in 2008.  If Obama ran ahead of the Senator or member of Congress, then conceivably they will feel a stronger obligation to support his congressional agenda. In contrast, if he ran behind the candidate, then they will be less likely to bend to his will.

Alas for Obama, as I noted in that earlier post, his Senate coattails were quite minuscule; he finished ahead of the winning Senate candidate in only 5 of 33 Senate races in 2008. (The five states in which Obama polled more votes than the winning Senate candidate are: Colorado, Minnesota, New Hampshire, New Jersey, and Oregon).

Of course, one could argue that Senate races tend to be less responsive to national trends because many states have very heterogeneous populations, Senators serve six year terms, and generally Senators tend to be more moderate ideologically speaking than their counterparts in the House. But what about the House?  Aren’t House elections more susceptible to national trends?  After all, House districts tend to have more homogenous populations, and members serving two year terms have to pay more attention to prevailing political winds. Surely Obama’s coattails are stronger in the House!

Using data gathered by the SwingState project, I recently did a back-of-the-envelope calculation to see in what percent of the 435 House districts Obama ran ahead or at least even with the winning congressional candidate (Democrat or Republican).

Before putting the numbers up, however, I’m interested in hearing your best guesses.  What do you think?  What percentage of House districts did Obama carry – that is, finished tied or ahead of the winning candidate – in 2008?  Remember, the media proclaimed Obama’s victory to be a “mandate” from the voters – an assessment that many of you shared.   How fully did that mandate impact congressional races?  Did he finish ahead in 50% of the races?  75%?

Give me your best guess (just respond in the comment sections to this post or directly by email to me).  The winner receives an “It’s the Fundamentals, Stupid” t-shirt.


  1. I’ll go with 15% (65 districts), keeping consistent with his “minuscule” Senate coattails. You wouldn’t be so obviously delighted if it were much higher, now, would you?

    And should I win, I would like to donate my t-shirt to VT’s Chief Executive, Gov. Douglas, in honor of the recent over-ride of his gay marriage veto.

  2. About 67 house seats changed hands, and only 30 of them were races in which the incumbent was running. The presumption has to be that an extremely large majority of the other races were won by large margins, given the huge advantages incumbents have.

    Of these 67 races, I’d guess that Obama did better than the winning candidate in only a fifth of those races.

    I’m going to go with 14 districts or just over 3%. I’d love for this to be an extremely low guess., but I think it’s relatively realistic…

  3. I am going to guess a total of five house candidates underperformed in their district against Obama. My Maine district (ME-1) was an open race and the Democrat won by a much larger margin than Obama, if I remember correctly. I bet that Obama stayed pretty close to the 50-55% win percentage in most districts, while most representatives won comfortably with 60-95% of the vote.

  4. “How fully did that mandate impact congressional races? Did he finish ahead in 50% of the races? 75%?”

    Since Obama lost nearly half of congressional districts it couldn’t be much more than half. And he probably lost to the congressional candidate in many districts he carried by >50%.

    So in total I’ll go with 8%

  5. I said “less than 10%, probably less than 5%” in response to a previous post. Since a few people are settled around 5%, I guess I’ll go with 3%, splitting the difference between Bob and Chris.

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