JEFFERSON CITY – Problems with polling site equipment in Missouri's most populous county led some voters to turn away in frustration Tuesday without casting ballots in a presidential primary that figured to further define the Democratic race between Joe Biden and Bernie Sanders.

After a rough start that affected at least the first hour of voting, St. Louis County election officials had reported no additional issues with their new equipment. But in the city of St. Louis, a polling place had to be closed after a man who had just voted backed his vehicle into the building, re-entered and began knocking over equipment.

No one was injured in the incident and police took the man into custody, but it took nearly an hour before voters could be redirected to another polling place, said St. Louis Election Director Gary Stoff.

"I don't think there was anything about his voting – at least he didn't give any indication – that caused him to explode the way he did," Stoff said. "Right now, we really don't know why."

It's unclear whether the unusual incident scared anyone away from voting. But earlier in the day, some voters did walk away after St. Louis County's electronic poll books, which are used to check in people, had trouble syncing with the county's system. The problem was compounded when some poll workers failed to switch to a manual system to print ballots.

"They got flustered," said St. Louis County Election Director Rick Stream. "Voters left, they had to go to work. That's on us, we should have had everything working properly."

Stream estimated that people had reported problems from at least 50 of the county's roughly 400 polling sites. He said problems could have occurred at more sites but just not been reported.

Kansas City Mayor Quinton Lucas also reported voting problems in his city – with his own ballot. Lucas said he struggled to vote at his polling site because workers couldn't find his name on the voter registration list. He said it turned out that his name had been entered backward – with his last name listed as his first name.

Despite some glitches, Missouri Secretary of State Jay Ashcroft said the primary election had gone fairly well, overall.

Missouri was among several states holding presidential primaries on Tuesday, along with Idaho, Michigan, Mississippi, North Dakota and Washington. Former Vice President Biden was looking to build upon the momentum from last week's primary victories in what has become essentially a head-to-head battle with Vermont Sen. Sanders.

But Missouri has a recent history of close Democratic primaries. In 2016, Sanders lost by fewer than 2,000 votes to eventual Democratic presidential nominee Hillary Clinton.

Some Missouri voters who cast ballots for Biden said they were doing so because they believed he could match up better against Republican President Donald Trump.

"The number one issue for me is electability, and I think Biden has a better chance of defeating Trump," said Donald Lancasty, a 69-year-old retiree who voted Tuesday at a church across from the campus of the University of Missouri-Kansas City.

Keith Williams, a 72-year-old Ferguson resident, also voted for Biden, citing his experience and likability. He's not so sure Biden, or anyone, will beat Trump, though.

"I'll vote for Biden in November, but I don't think Trump will lose," said Williams, shaking his head.

Patrick Sanders, a 22-year-old English student at the Kansas City university, said he voted for the presidential candidate with his same last name, partly because of his ideas for expanding health care coverage.

"There is a shot with him of something that is different, that is much more hopeful than what we have now," Sanders said.

Concerns about the coronavirus forced some late scrambling of plans in Kansas City and St. Louis County, when two senior living facilities backed out of serving as voting sites less than 24 hours before the polls opened. Election authorities posted signs at the facilities redirecting voters to a nearby church in Kansas City and a union hall in the St. Louis suburbs. About 150 of the 3,200 poll workers in St. Louis County canceled shortly before the election because of coronavirus concerns, as did 77 of the roughly 800 poll workers in Kansas City, local election officials said.

Some polling places provided hand sanitizer for voters and stocked up on disinfectant wipes for the equipment and pens. Greene County Clerk Shane Schoeller said special gloves were available for people to sign in or vote on touchscreens, and voters also were welcome to bring their own pens to mark paper ballots.

"We want them to feel comfortable exercising the right to vote," Schoeller said.

Whoever wins the Missouri primary could face an uphill battle to carry the state in November against Trump. The last Democrat to carry Missouri was President Bill Clinton, in 1996. Barack Obama narrowly lost in Missouri in 2008, but the state has turned decidedly Republican since then. Mitt Romney carried Missouri by 9 percentage points in 2012, and Trump won the state by 19 percentage points on the way to victory in 2016.

Missouri was long considered a bellwether state until the recent trend. Missouri voted for the winning presidential candidate every time but once in the 1900s, missing only in 1956 when it picked Democrat Adlai Stevenson instead of Republican President Dwight Eisenhower.

Salter reported from St. Louis. Associated Press writer Heather Hollingsworth and Margaret Stafford in Kansas City contributed to this report.