holds a dominant position in national polls in the Republican race in no small part because he is extremely strong among people on the periphery of the coalition.
He is strongest among Republicans who are less affluent, less educated and less likely to turn out to vote. His very best voters are self-identified Republicans who nonetheless are registered as Democrats.
In many of these areas, a large number of traditionally Democratic voters have long supported Republicans in presidential elections. Even now, Democrats have more registered voters than Republicans do in states like West Virginia and Kentucky, which have been easily carried by Republicans in every presidential contest of this century. As recently as a few years ago, Democrats still had a big advantage in partisan self-identification in the same states.
But during the Obama era, many of these voters have abandoned the Democrats. Many Democrats may now even identify as Republicans, or as independents who lean Republican, when asked by pollsters — a choice that means they’re included in a national Republican primary survey, whether they remain registered as Democrats or not.
Mr. Trump appears to hold his greatest strength among people like these — registered Democrats who identify as Republican leaners — with 43 percent of their support, according to the Civis data. Similarly, many of Mr. Trump’s best states are those with a long tradition of Democrats who vote Republican in presidential elections, like West Virginia.
Mr. Trump’s strength among traditionally Democratic voters could pose some problems for his campaign. Many states bar voters registered with the other party from participating in partisan primaries. Other states go further, not allowing unaffiliated voters to vote in a primary; in the G.O.P. race, for example, that would mean restricting the electorate to those registered as Republicans — one of Mr. Trump’s weakest groups. This group of states includes many favorable to Mr. Trump, like Florida, Pennsylvania and New York.