The Supreme Court’s Colorado Trump Test

Donald Trump and his opponents have embroiled the Supreme Court in this year’s election politics, and the Court’s first test comes Thursday when the Justices consider the Colorado Supreme Court’s decree barring the former President from the state’s ballot. The Justices can help democracy with a unanimous ruling against Colorado.

The Colorado court voted 4-3 in December to disqualify Mr. Trump under Section 3 of the post-Civil War 14th Amendment, also known as the Insurrection Clause. The four Justices held that Mr. Trump engaged in an “insurrection or rebellion” on...