This story was updated at 4:55 p.m.
Days before Missouri holds its Democratic presidential primary, former Vice President Joe Biden has a slim lead over Vermont Senator Bernie Sanders, according to a poll released Thursday.
The Emerson College poll has Biden with 48% and Sanders with 44%. That is within the poll's 4.7% margin of error.
The poll was conducted before Sen. Elizabeth Warren dropped out Thursday. But Warren supporters are leaning towards Sanders, according to the poll. "A majority, 53%, said that Sanders was their second choice, followed by 32% who said Biden was their second choice," Emerson said in an analysis released with the results.
There are also differences in the two candidates' support regionally around the state.
Biden receives overwhelming support in St. Louis with more than a 30% margin over Sanders. Biden also does well in mid-Missouri.
But Sanders leads in the northern and southern parts of the state, but his margin is much smaller in those places than the one Biden has in St. Louis.
"It appears the Kansas City area is the battleground in Missouri as Biden leads 49% to 46%," according to the analysis.
Biden is set to appear at an event at the Liberty Memorial Saturday. On Friday, Sanders cancelled a rally planned for Monday at the Midland Theater "due to scheduling constraints." Instead, Sanders will hold a rally in St. Louis.
"All candidates have a level of field operation here," state Democratic Party Chair Jean Peters Baker told KCUR.
Baker said she has been in contact with both campaigns.
"I'm telling them who they should be talking to," she said. "And what parts of this state I think are particularly of concern to them."
Almost a third of Missouri Democrats say health care is the most pressing issue. Forty-three percent of respondents said Sanders has the best health care plan. Almost 40% go with Biden on that issue.
Sanders has touted his Medicare for All plan, and almost 43% of those surveyed back that idea. About 27% want a public option. Only 10% want to keep health care policy the same.
The Missouri primary is Tuesday. Polls are open from 6 a.m. to 7 p.m.
Sam Zeff is KCUR's Metro Reporter. Follow him on Twitter @SamZeff