There will be no immediate answer on how Missouri replaces a lieutenant governor who leaves partway through a term.
Gov. Jay Nixon vetoed legislation that would require a new lieutenant governor to be selected during the next general election, while an aide for the departing officeholder handles the office's duties in the meantime. Under the vetoed bill, the lieutenant governor's responsibilities as Senate president were to be handled by a senator.
Nixon says the measure would have created a "confusing and untenable process."
Missouri governors appoint replacements to other statewide offices, but there has been uncertainty about how the lieutenant governor should be succeeded.
Congressman Jason Smith sponsored the legislation. He criticized the veto and says voters should be able to elect a new lieutenant governor.