But the Constitution does not address how a lieutenant governor should be replaced if a vacancy occurs.
The Constitution says the governor shall fill all vacancies in public office "unless otherwise provided by law," and those appointees shall serve until their successors are duly elected.
But a section of Missouri law seems to carve out the lieutenant governor from that provision, saying the governor can fill all vacancies "other than in the offices of lieutenant governor, state senator or representative, sheriff, or recorder of deeds in the city of St. Louis."
State law lays out that legislative vacancies are filled through special elections, but offers no specifics about how the lieutenant governor is to be replaced.
In the modern era, the situation has only happened twice.
The first came in 1969, when Lt. Gov. Thomas Eagleton resigned shortly before the end of his term so that he could be sworn in as U.S. senator.
Lt. Gov.-elect William Morris was appointed to serve out the final days of Eagleton’s term, which ended on Jan. 13, 1969, the same day that Morris would be sworn-in for the full term he'd won in November.
The first day of the legislative session that year was Jan. 8, 1969 — five days before the beginning of Morris’ full term.
Senate leaders, who believed vacancies in the office of lieutenant governor couldn't be filled, said the appointment of Morris was illegal and threatened to have him thrown out of the chamber if he tried to preside over the Senate on the first day.
Morris didn’t preside until he was sworn in to his full term the next week.
In 2000, Lt. Gov. Roger Wilson became governor after the death of Gov. Mel Carnahan in a plane crash. State Sen. Joe Maxwell subsequently won election as lieutenant governor in November 2000.
Wilson appointed Maxwell to serve out the final weeks of his term as lieutenant governor, and no one disputed the appointment or tried to bar Maxwell from presiding over the Senate at the start of the 2001 legislative session.
No lawsuits were filed challenging either the Morris or Maxwell appointments, so the Missouri Supreme Court has never addressed the issue.
Parson said Monday that he believed the Constitution gave him the authority to appoint Kehoe as lieutenant governor. He pointed to the comments of four former governors — Jay Nixon, Matt Blunt, Bob Holden and Roger Wilson — to buttress his argument.
"The lieutenant governor position is an important position," he said, "not just because of duties assigned by Missouri law and the state constitution, but also to reassure Missourians that all operations of state government will continue.”