I'll agree that he confused the issue by mentioning Clinton resigning in 1998 to begin with.
Furthermore, he erred by stating that the Democrats would have retained control of the Presidency for an additional 8 to 10 years.
That's because they had control for the duration of Clinton's term regardless who served that term out.
Thus the Democrats would have only gained 4 more years, if he had resigned and Gore won election to serve the limit he could legally serve after taking over for Bill Clinton. Or 8 more years had he been removed from office & Gore served 2 additional terms in addition to completing the term that started with Bill Clinton as President.