This wasn't a mandate.
It was a 51-48 win. It was a win of 3 points. A solid win, but no mandate. If you congratulated Bush for getting the highest popular vote ever, you must consider George Washington's election a miserable failure.
A mandate is a matter of degree. A majority of the vote provides more of a mandate than a plurality, especially when everybody knows what you stand for, and voted accordingly.
You probably thought that Clinton's 43% of the vote in 1992 represented a mandate. That's usually how these things work - the person you want always has a mandate, while the opponent never does.