Secretary of State Jay Ashcroft said Monday that 54.73 percent of Missouri's 4,213,092 registered voters likely will have cast ballots by the end of today's election.
Polling places opened at 6 a.m. and will remain open until 7 p.m.
Ashcroft's news release reminded voters that those "in line at 7 p.m. are qualified to cast a ballot," even though the doors will be blocked for latecomers.
Cole County Clerk Steve Korsmeyer told the News Tribune on Monday afternoon he remains confident in his prediction that 55 percent of the county's 53,232 voters will cast ballots.
"I won't be surprised if it is a bit higher, though," he added. "We have had 3,175 absentee received" as of 5 p.m. Monday, when in-person absentee voting ended.
He added, "(We) may receive some (today) in the mail. All absentee ballots must be received in our office by 7 p.m.," when the polls close.
The new statewide voter registration number was as of Nov. 1, and showed a drop of 10,695 voters from the number that were registered two years ago, for the general election that included national voting for the nation's president and vice president.
If the statewide turnout prediction for this election is accurate, then only 2,305,825 people statewide will cast ballots in this election - nearly a half-million people fewer (498,410) than voted in 2016.
Numbers released by Ashcroft's office going back to 2000, and additional statistics reported in the state's Official Manual (Blue Book) going back to 1990, show several general trends.
The number of registered voters generally has been rising over the last 29 years - although every mid-term election but one involved fewer registered voters than those who had signed up to cast ballots in the presidential election two years earlier.
That one exception was 1998, when Missouri's statewide voter registration rose by 293,702 voters - then rose again, by another 224,681.
Since 2006 - when the state's records first show a pre-election prediction as well as the actual turnout - the prediction always has been higher than the actual turnout, except in 2006 when the prediction was 4 percent lower than the final number of voters.
However, one trend has had no exceptions during the three decades covered by this story - the percentage of voters casting ballots in the mid-term elections, like this year, has been smaller than the percentage of voters in presidential years.
Although no one offered a definitive reason, it generally is assumed American voters believe they have more impact when choosing the president and vice president than when voting for state or local offices.
And the margins are pretty wide.
In the presidential election years, at least 61.2 percent of Missouri registered voters turned out in 2000 - an election marred by, and likely affected by, then-Gov. Mel Carnahan's death in a plane crash only three weeks before the election, as he was running for the U.S. Senate against incumbent Republican John Ashcroft.
The highest percentage of voters in the period since 1990 came in 1992 - 77.94 percent - when H. Ross Perot led an Independent challenge to Republican President George H.W. Bush's bid for a second term and Democrat Bill Clinton's ultimately successful effort to disrupt the GOP's decade-long control of the White House.
Second highest on the list was two years ago, when 66.56 percent of Missouri's registered voters cast ballots in an election that saw Republicans generally solidify their veto-proof majority in the Legislature, capture all five of the statewide offices that were on that ballot and, nationally, kept control of Congress while also winning the White House.
The only Democrat serving at the top of state government today is Auditor Nicole Galloway - a Democrat and one of five people on today's ballot who are seeking to head the state's accounting, watchdog agency.
During the mid-term elections since 1990, the lowest percentage of Missourians voting came in 2014, when only 35.32 percent cast ballots.
The highest mid-term participation came in 1994, when 60.12 percent of the state's registered voters cast ballots.