There is a clip on youtube that showed a Gallup Poll from October 1992 before the first debate. It was...
Clinton - 52%
Bush - 37%
Perot - 9%
So if the final was...
Clinton - 43%
Bush - 37%
Perot - 19%
Wouldn't that mean that most Perot voters would have been Clinton voters in a two-way race?
Let's not forget the 1996 election also went like this:
Clinton - 49%
Dole - 40%
Perot - 9%
With Perot being less of a factor, Clinton's margin of victory was greater.
Basically D-leaners who supported Perot in 1992, returned to the Democratic fold in 1996.