Response:
Responding to the Paul ad, a source close to the Perry campaign points out that Perry was a conservative Democrat at the time, and Gore, then a senator from Tennessee, was considered the most conservative of all the candidates running for the 1988 Democratic presidential nomination.
And the campaign itself put out a statement Tuesday afternoon saying "Rep. Ron Paul's newly released attack ad refers to the congressman as, 'the one who stood with Reagan.' But his 1987 letter announcing his resignation from the Republican Party indicates Reagan drove him from the party."
The Perry campaign email release includes Paul's resignation letter. Paul ran for president in 1988 as a libertarian.