The two major party Presidential candidates have them.  All Presidents and candidates who wish to nominate Supreme Court Justices have them; some are more or less legitimate than others.

Democratic Party Presidential candidate Hillary Clinton’s wants:

The kind of people that I would be looking to nominate to the court would be in the great tradition of standing up to the powerful, standing up on behalf of our rights as Americans[.]

Read that again.  Clinton wants Justices who put social agendas ahead of the actual law before them, ahead of the text of the Constitution, ahead of the Justices’ own oaths of office, which swear them to uphold and defend the Constitution, not ignore it, or “reinterpret” it.

Republican Party Presidential candidate Donald Trump’s wants:

[Justices who would] interpret the Constitution the way the founders wanted it interpreted.

Notice that.  Justices who will do the opposite of what Clinton’s choices will do: rule on the basis of what the law and the Constitution actually say, rather than on what the Justices might wish had been said.

There’s just one more litmus test that I would add, one as general and carefully nonspecific as Trump’s: lose deference to the other branches of the Federal government.  The founders also wrote the Judicial branch as the equal of the Legislative and Executive branches.  No deference is owed, no deference is legitimate.  Deference subordinates what is intended to be a coequal branch of the government to the other two.  Besides, a law is Constitutional, or it is not; that does not depend in any way on who says it.   Further, a matter before the Court comports with the law and the Constitution on its merits, or it does not; that does not depend on who is bringing or defending the matter.

One of these two will be nominating Justices in the next term—at least one, likely three, and maybe four or five.  The next President will determine the tenor of the Court and the viability of our legal system for generations.

It’s clear which set of choices are better for the present and long term health of our nation.