Just under half of white voters supported Trump; nearly one in three supported Clinton, with one in 10 supporting Johnson and a similar percentage undecided. Clinton got the support of virtually all the black respondents.

One significant finding: One in 10 self-identified Republicans favored Johnson, the former governor of New Mexico. One of six independents said they supported Johnson.

Virtually no Democrats said they supported Johnson. Clinton has the support of almost nine of 10 Democrats.

Coker said the Missouri outcome hinges heavily on whether Johnson is included in presidential debates, threatening Trump’s support, and on how many disaffected Democratic supporters of Sen. Bernie Sanders either don’t vote or gravitate to Green Party candidate Jill Stein, who barely showed up in his Missouri poll.

“You have the ‘never Trump Republicans’ … looking at Gary Johnson,” Coker said. “Get to the fall and everybody’s perspective changes. If Johnson is not in the debates, then people will think they are wasting their votes. But if he is in the debates and he doesn’t do badly, he might just be able to hold something in the mid-teens or maybe get close to the 20s, if people hate Trump and Clinton then as much as they do now.”