[PBRCat]

Not a bad article, but the columnist omitted to add that former President Andrew Johnson actually did serve in the Senate (briefly) after leaving the White House.

[Salena Zito]

I wrote it and yep, I forgot old Andy. My bad.

[TBP]

And John Quincy Adams served in the House after he had been President. He even died in the House cloakroom.

FWIW, johnTyler served in the Cofederate Congress.