@Lilkanyon,
Yes, Bernie splitting off to a third party, (actually too late to do that and get on the ballot in most states), might well cause Hillary the election if it happened.
Perot did not cause Bush 41 to lose the election in 1992 because Perot was not identified as a Republican who was breaking away. He was a complete independent, and while he might have been a registered Republican the public did not know him as one, he never ran for office or got involved in any Republican campaigns that anyone remembered.
As proof, consider this. In 1992, Ross Perot got 19% of the vote, and the Democrat, Bill Clinton, won by 6 percentage points over the Republican, Bush 41. In 1996, Perot ran again, this time took public camapaign money which limited his funding, and and so he only got 8% of the vote-less than half of what he got in 1992. But Clinton beat the Republican, Bob Dole-by 9 points! The lesser percentage of votes that Perot got, the higher the percentage of votes Bill Clinton received.
That would not happen if Perot was mostly taking votes from the Republicans.