Instead, our undecided voters just don’t know much about the candidates: 56 percent of the undecided voters don’t know either candidate, while only 17 percent of decided voters don’t know either candidate.

Over all, 70 percent of decided voters like at least one of the candidates in their districts. Just 20 percent of undecided voters like at least one of the candidates.

A narrow category of undecided voters seems not to like either candidate: 11 percent of undecided voters don’t like either candidate, something true of only 4 percent of decided voters.

This probably isn’t unusual for these voters. Their lack of knowledge probably reflects a generally lower level of political engagement. A majority of the undecided voters in our polling have never voted in a primary before. Just 50 percent say they’re almost certain to vote in November, compared with 67 percent of decided voters.

Demographically similar, but more diverse and less educated

Undecided voters don’t look vastly different demographically from decided voters, but there are some minor differences. They’re likelier to be women. They’re likelier to be nonwhite. They’re also less likely to be college graduates.

White college-educated voters are particularly underrepresented among undecided voters: They make up 39 percent of decided voters, but just 32 percent of the undecided.

This subtle demographic difference plays out in geographically significant ways.

Democrats seem to have a lot of upside in the Sun Belt districts where Democrats are dependent on nonwhite voters and where there are relatively few white working-class voters. Over all, the undecided voters in the Sun Belt districts are 50 percent white, compared with 62 percent of decided voters. Hispanic voters make up 35 percent of undecided voters, compared with 25 percent of those who are decided.