More political science geek ranting:
Why does America have a two party system? Why has there never been a third party president? Because it’s an unintended consequence baked into the Constitution.
Look at countries with stable, multiple-party systems: Canada, Germany, the United Kingdom, Israel. What do they all have in common? They’re Westminster-style parliaments, meaning the head of government (the prime minister or chancellor) is elected by majority vote of the legislature. That means minor parties that can never win a majority on their own can wield power by winning enough seats that a major party will have to form a coalition with them in order to form a government. The minor party then gets rewarded with cabinet seats and power over the major parties’ agenda. If the major party goes too far, the minor party can threaten to leave the coalition and cause the government to fall.
The United States by contrast has a unitary executive (the president is both head of government and head of state) who is elected separately from the legislative branch. That’s why we can and frequently do have divided government, one party controlling Congress and one the White House, something unheard of in other countries. Coming in second in a presidential election gets you exactly the same as coming in third or twentieth: nothing. How much influence did George Romney or John McCain have in the Obama Administration? George W. Bush lost the popular vote in 2000 but you didn’t see him appointing Al Gore to the cabinet. Since there’s no reward for almost winning a presidential election, third parties can’t really do much of anything except (rarely) serve as spoilers.
So should third parties just give up? Not necessarily but they should stop wasting scarce resources on vanity presidential campaigns that are never going to win. Instead, in my opinion, they should concentrate on House elections. Coalitions matter in the House, since the Speaker is elected by majority vote. The last really successful third party, the Populists, wielded at least some power in the late 19th and early 20th Centuries by winning seats in Congress, while never really getting that close to the White House. Thanks to modern, hyper-partisan gerrymandering, the majority of House districts aren’t the least bit competitive. This suggests that a party like the Libertarians might win in some Republican districts with a coalition of Democrats and Republicans who are put off by social conservatism and the Religious Right. There might be some Democratic districts where Greens could be competitive, though that seems less likely.
Sadly for them, the Libertarians have blown a golden opportunity to at least make a decent showing this year. With two historically unpopular major party nominees and most Americans desiring change, the Libertarians are getting more media attention, and thus more free publicity, than at any time in their history, maybe more than any third party candidate since Ralph Nader or H. Ross Perot. Rather than capitalize on this, they nominated a doofus like Gary Johnson who consistently embarrasses himself every time he’s interviewed by stumbling over softball questions and then poutily declaring that his ignorance is somehow a virtue. They’d have been better off with former Massachusetts Governor William Weld at the top of the ticket, but instead he’s pretty much written the whole thing off to concentrate on defeating Donald Trump. Yet another example of how third parties can’t seem to win for losing.