The paradox is that the voters reward economic upswings, but historians look for leadership of vision. Reagan's legacy is not affected by whether his tax policies worked, and everyone agrees that FDR mitigated the Depression at best until the War came along.
Clinton's shot is that historians will forgive his lack of domestic progress *because* of the economic boom. If you're not in office during a crisis of some kind, historians tend to give you a pass, because challenges make presidencies. Clinton led America during the single most challenge-free era since maybe the first decade of the 20th Century.
Or so we thought at the time. Whether he'll be punished for not doing more against islamist terror remains to be seen. His defender unfortunately cannot claim that he was unaware of the threat. he did just enough to disqualify that argument.
I will say this: had Arafat not fucked him at Camp David, Clinton's legacy would look a whole lot better right now.