From a 1968 Supreme Court Decision
Over thirty years ago, no less a body than the United States Supreme Court suggested using the instant runoff to encourage effective political participation while ensuring majority rule. State legislatures ought to take the Court's advice and give voters the right to indicate their second-choice candidates on Election Day.
Justice Harlan is grappling with the State of Ohio's defense of its extremely restrictive ballot access regime. Ohio claims that it has a valid state interest in keeping third parties off the ballot, because with three candidates the winning candidate often receives less than a majority of votes. Harlan writes:
"My Brother STEWART is, of course, quite right in pointing out that the presence of third parties may on occasion result in the election of the major candidate who is in reality less preferred by the majority of voters. It seems clear to me, however, that many constitutional electoral structures could be designed which would accommodate this valid state interest, without depriving other political organizations of the right to participate effectively in the political process. A runoff election may be mandated if no party gains a majority, or the decision could be left to the State Legislature in such a case. Alternatively, the voter could be given the right, at the general election, to indicate both his first and his second choice for the Presidency -- if no candidate received a majority of first-choice votes, the second-choice votes could then be considered."
Williams v. Rhodes, 393 U.S. 23, 47 FN. 8 (1968) (J. HARLAN, concurring).