Erin Kelly

USA TODAY

WASHINGTON — Voters again turned out in record or near-record numbers Tuesday in five key primary elections, continuing a pattern of very high participation that has played out during the 2016 election cycle.

Missouri Secretary of State Jason Kander announced Wednesday that the unofficial voter turnout in the presidential primary was a record 39%. More than 1.5 million registered Missouri voters turned out to nominate candidates for president, Kander said. The 2008 primary set a state record with approximately 1.4 million votes and a 36% turnout.

In Ohio, the turnout was the second highest in a primary contest, election officials said. It was about 41%, just 5 percentage points shy of the 46% turnout record set in 2008.

North Carolina election officials also said their primary turnout was the second highest in the past 28 years. The turnout was about 35% on Tuesday. A record turnout of 37% was set in 2008.

In Florida, about 46% of eligible voters cast ballots in the primary contest, which Donald Trump and Hillary Clinton won. Florida Sen. Marco Rubio suspended his campaign after losing his home state primary. The turnout was higher than in the Republican-only primary of 2012 and the joint primary of 2008, when 42% of eligible voters participated, according to the Florida Department of State.

Illinois was still calculating turnout Wednesday, but the United States Elections Project estimated that the state's turnout was up about 19 percentage points from 2012 and about 3 percentage points from 2008. The project's website, which is run by Michael McDonald, an associate professor of political science professor at the University of Florida, said the estimated turnout is based on the total number of ballots counted in each state divided by the voting-eligible population.

Top takeaways from 'home-turf' Tuesday

This year's primaries have sparked record turnout by Republican voters and stronger-than-usual turnout by Democratic voters, according to an analysis by the Pew Research Center.

More than 17% of eligible Republican voters participated in the first 12 primaries of 2016 — the highest turnout since at least 1980, the Pew Research Center analysis shows. Nearly 12% of eligible Democratic voters also turned out, the second highest percentage in the past 24 years. The highest turnout for Democrats in recent years was in 2008, when nearly 20% of eligible voters came out to choose between Obama and Clinton.

Political scientists say Republican turnout is higher this year in part because the GOP primaries are viewed as more competitive than the Democratic contest, where Clinton has dominated the race for convention delegates despite some surprise upsets by Vermont Sen. Bernie Sanders.

"People will vote if the election is close or expected to be close and if voters perceive real differences among the candidates," said McDonald, who is also a senior fellow at the Brookings Institution. "Republicans have both of those things going for them right now."

The angry split between Trump voters and those who support "establishment" Republicans stands in stark contrast to Democratic voters, who are much more unified, McDonald said.

"More than 70 percent of Democrats, in exit polls, said they would be satisfied if either Clinton or Sanders were their candidate," he said.

Tuesday primaries: State-by-state roundups and results

The polarizing nature of Trump's candidacy has helped drive GOP voters to the polls, spurring participation from passionate supporters and fierce opponents, said Steven Taylor, a professor and chairman of the political science department at Troy University in Alabama.

"There's no question that Trump excites people and motivates them to turn out to the polls, whether it's to vote for him or against him," Taylor said.

He said there is not yet enough data to support Trump's claims that he is turning out millions of new voters.

"Are they truly new voters? Were they going to stay home if Trump wasn't on the ballot? We don't really know yet," Taylor said. "We need to ask detailed questions in exit polls about who is a first-time voter and look at their ages and demographics."

Analysis: Victorious or not, no end in sight for Clinton or Trump

While Republicans boast of stronger participation by their primary voters, there is no correlation between primary turnout and which party is going to win the general election, political scientists say.

An analysis by Politifact of presidential elections going back to 1972 showed that the party with the highest percentage turnout in the primary races won the White House only four out of 11 times.

"You can't predict who is going to win the presidency based on turnout in the primaries," McDonald said. "It's an unfair comparison."

Historically, many more people turn out to vote in the general election than in the primary races, Drew DeSilver of the Pew Research Center wrote in an analysis of this year's election data. In the 2012 presidential election, more than 129 million Americans voted in the general election, compared to 28 million who voted in the primaries, DeSilver noted.

"Even in relatively high-turnout years such as 2008 — and, so far, 2016 — primaries attract far fewer voters than general elections, even though...they determine whom voters get to choose from come November," DeSilver said.