In 1860, Democrat John Bell split the Democratic Party into Northern and South wings. He tipped the election to Republican Abraham Lincoln.
In 1912, Republican Teddy Roosevelt ran as the "Bull Moose Party" candidate. He tipped the election to Democrat Woodrow Wilson.
In 1968 Democrat George Wallace ran as a third party. He tipped the election to Republican Richard Nixon.
In 1993 Independent Ross Perot ran as a third party. He tipped the election to Democrat Bill Clinton.
Since the modern party system was created with the establishment of the Republican Party in 1856, these are the four "third party" campaigns that garnered enough votes to get into the history books. Just about every election had third party candidates but mostly they never garnered enough votes to matter. These are the four big third party campaigns that did well enough to matter.
In all four cases, the third party was a split off from either the Democrats (Bell and Wallace) or the Republicans (Roosevelt and Perot). In each case the presence of the third party campaign tipped the election to the other side.
So today we have unhappy Republicans talking up a third party campaign. If they get it off the ground, history says it will tip the election to the other party, Hillary.
I don't want Hillary as president. The Donald would be much better.