Because Perot did nothing of the kind. Every poll shows that Clinton would have gotten a majority or even two-thirds of the Perot vote in 1992. In many ways, Perot hurt Clinton, since he denied Clinton the mandate of a majority victory. There is also good evidence that Perot undermined Democratic Senate races, especially in 1996, where voters who probably would have voted for Clinton and then for a Democrat, found it easier to split tickets between Perot and then a Republican for a lower level office.
-- Nathan Newman