Questionable Claim in Left Turn

On page 52 of Left Turn, Tim Groseclose claims that most nonvoters are moderates in order to rationalize not accounting for nonvoters in his model: "Even if we could force all of these people to vote, then it is doubtful that they would overwhelmingly vote for the Democrat. More likely, since they are approximately indifferent, they would approximately split their votes between the Republican and the Democrat."

I was surprised by this comment because I think of nonvoters tending to be minority members of the population who would probably support liberal policies and political candidates if they were to vote. I looked up research from the Pew Research Center and found data that supported my hypothesis:

As one can see, nonvoters are younger, earn less, and are more likely to be Hispanic than likely voters on average. As a result, nonvoters were more likely to support Obama than likely voters in the 2012 election (59% versus 47%). This data persuades me to object to Groseclose's argument that the average nonvoter is equally likely to support a liberal or conservative candidate.