This graph suggests a linear relationship between ideology and electability. Moving from the most moderate Republican candidate — Christie — to the most conservative — Cruz — diminishes GOP prospects for winning the presidency by 23 percentage points. And if we compare the two candidates most likely to win the nomination according to Betfair, the more conservative Rubio is 9 points less likely to win the general election than the more moderate Bush.
It may be surprising that Chris Christie emerges as so electable in this analysis. Why would someone as apparently electable be doing so poorly in the primary polls? It’s likely because Christie has more potential appeal to the average voter in the national electorate than the average voter in Republican primaries. In other words, the Republican Party would be rewarded in the general election for nominating someone, like Christie or perhaps even Bush, that is less palatable to their rank-and-file voters.
The rewards of nominating a relative moderate apply to the Democratic Party as well. Of the three candidates under serious consideration, Bonica’s ideology scores deem Sanders the most liberal and Biden the most moderate, with Clinton in between. The Democratic Party’s penalty for nominating Sanders over Biden is a 10 percentage point decline in the probability of winning the general election.