Coattail Effect: How far can a Governor's job approval carry his or her party's presidential nominee?

Governor Bob McDonnell (R) (left) has an enviable 51/29% job approval rating back home in Virginia, yet the Republican candidate for President lost to the President by 3 points. Meanwhile, Wisconsin GOP Governor Scott Walker (right) had a decent 51/46% job rating, yet Romney lost his state by 7 points.

Virginia Governor Bob McDonnell became one of the most prolific campaign surrogates in the 2012 election, crisscrossing the country on Mitt Romney's behalf. Not only was he a popular home-state Governor, but he just happened to be the chief executive of one of the most hotly contested swing-states in the nation. That's a helpful combination to have around. While popular Republican governor's like Chris Christie and Susana Martinez were good faces to have associated with the Romney campaign, their home-states of New Jersey and New Mexico were never really in contention. They didn't pack the same one-two punch of Virginia's Bob McDonnell.

Obviously, there's a reason we seldom saw or heard of Florida Governor Rick Scott barnstorming across the state with Mitt Romney, or Pennsylvania Governor Tom Corbett holding local town-halls with Paul Ryan. Both of them averaged 39/45% and 35/46% job approval/disapproval ratings respectively in the final two months of the campaign.

But does the actual evidence suggest that a Governor's job approval/disapproval rating can affect Presidential election results on a state level? Unfortunately, the data is not terribly clear.
The table below contains a lot of information, so let's break it down piece by piece. It compares the job approval/disapproval ratings for every U.S. governor over the final two months of the 2012 Presidential campaign to actual election results, as well as actual election results to Obama/Romney's favorable/unfavorable ratings. In order for a particular state Governor to be included in the chart, he or she must have had at least one job approval assessment in the September and October before the election. That's why a few Governors, like Alabama, Mississppi, Wyoming, etc are missing. Red entries indicate either a Republican Governor, a Republican election win, or a net state-based positive favorability rating for Mitt Romney in the presidential election. Likewise, blue entries indicate Democratic Governors, a Democratic election win, or a net state-based positive favorability rating for Barack Obama. Since exit polling was only conducted in 31 states in 2012, not every state will include an Obama/Romney favorability assessment. Polling information was compiled from tpm poll tracker, pollster, and various internet searches:

For an easier to read, larger version of the above table, click here.

Of the top 10 most popular Governors in the country (based on polling averages taken from September 1-November 6 2012), 5 were Democrats, and 5 were Republicans, in 5 blue states, and 5 red states. Of the 10 least popular, 5 were Democrats, 4 Republicans, and 1 liberal Independent, in 9 blue states, and 1 red state. This stat seems to suggest red-state residents (those states that voted for Romney in the last election) tend to be bigger fans of their Governors (whether they be Democrats or Republicans) than blue state residents.