“Liberal” and “conservative” are imperfect labels subject to change where the high court is concerned, and that is illustrated by the longest-standing Democratic litmus test: upholding Roe v. Wade. Nothing about the Fourteenth Amendment’s text or history in the century after its 1868 ratification suggested it dictated the nationwide legalization of abortion, which had been established as a crime under both common and statutory law and accepted as such by the giants of the Supreme Court.

The latter category included Justice John Marshall Harlan, the great dissenter from the “separate but equal” holding of Plessy v. Ferguson. It also included Louis Brandeis—author of the landmark Olmstead v. United States dissent asserting “the right to be let alone”—who along with Oliver Wendell Holmes joined a unanimous decision upholding the revocation of a doctor’s license for performing an abortion.

For that matter, even members of the Roe Supreme Court, including modern liberal champions William Brennan and Thurgood Marshall, would fail still another litmus test: A mere three months before announcing the abortion decision, the Supreme Court summarily rejected the claim of a same-sex couple that the Constitution gave them a right to marry, declining to take seriously the argument that would become law in Obergefell.

All of this highlights a problem with the ever-changing interpretation of the Constitution Senate Democrats promote: It imposes litmus tests nearly every justice who is not currently serving would fail, from the giants of the more distant past to recent liberal heroes.