Even if Congress doesn’t ban Trump from running again via impeachment, his comeback could be stopped in the courts, as some argue his incitement to insurrection in the Capitol riot makes him subject to a 14th Amendment ban meant for Confederates.
No Person shall be a Senator or Representative in Congress, or elector of President and Vice-President, or hold any office, civil or military, under the United States, or under any State, who, having previously taken an oath, as a member of Congress, or as an officer of the United States, or as a member of any State legislature, or as an executive or judicial officer of any State, to support the Constitution of the United States, shall have engaged in insurrection or rebellion against the same, or given aid or comfort to the enemies thereof. This clause of the 14th Amendment (passed in June of 1866 and ratified in July of 1868) was intended to bar ex-Confederate military officers and civilian officials from holding political office at a time when then-soon-to-be-impeached President Andrew Johnson was handing out pardons to former rebels like candy. The section goes on to provide that this “disability” can be waived via a two-thirds vote in both houses of Congress. That happened for most ex-Confederates via the Amnesty Act of 1872, and for all but a few of the highest-ranking rebels in later amnesty legislation in 1875.
