If that were the case anymore, it would’ve happened after the 1912 election when Theodore Roosevelt’s Progressive party got more votes (27.4%) and electors (88) than the Republican Taft (23.2% of the vote and 8 electors). But it didn’t. Things went back to normal after that. That was also the election where the Socialist party gained the most votes (6% of the vote and 0 electors).
The Republicans and Democrats are here to stay until our voting system is overhauled.