Are approval ratings and election results considered comparable?

Question

A recent Washington Post piece, Why Republicans feel so good about the 2014 midterms, in 1 chart, there is a (rather poor) chart showing the difference between Obama's 2012 election vote percentage and his current approval rating percentage, as a leading indicator for the 2014 elections. I thought it strange to compare the two percentages, but the columnist only glosses over the "theoretical" possibility of someone whose vote in an election doesn't match their approval rating.

Is there precedent for comparing approval ratings and election results? Or for doing so with adjustments. Surely past approval ratings are available, even for a more comparable time (six months before the election), and would support a similar if slightly weaker conclusion.

Answer 1

Approval ratings and election results measure a bit different things, and (at least) in two major cases they'll show different results :

1. Approval rates of both/all parties are correlated - if people believe that 'everything is bad nowadays', then they'll have lower approval rates for the president - but lower approval rates for the opposing officials as well. This will mean a change in approval rates without a corresponding change in viting preferences.

2. "All people" and "voters" are different populations. A very large portion of people simply don't vote, and likelihood of voting is not evenly distributed. Approval ratings usually try to measure the whole population, but in elections you measure only those who actually bother to vote, and these groups have a bit different opinions.