Another way we as American voters are limited in choosing the president of the United States is from what we see and hear (or don't see and hear) on TV - especially when tuning in to see and hear the presidential debates, which occurs every four years.
The presidential debates are relatively new. Major presidential nominees did not generally debate publicly until 1960 when Richard Nixon and John F. Kennedy faced one another on network television. While the 1960 debate could have had additional candidates present, Congress intervened and suspended the equal time provision of the Communications Act of 1934. Interestingly enough, this law stated that a broadcasting station permitting a candidate use of its facilities also had to grant the same opportunity to all other candidates, including minor candidates. But the government - especially the two major parties in charge - didn't want the public to see and hear different options; thus the oddly timed suspension of a federal law.
In 1970, Congress - again, with the two major parties leading charge as always - attempted to repeal the equal time provision of the Communications Act. But Nixon, oddly enough, vetoed it. Two years later, the U.S. Senate attempted to repeal it, but the House of Representatives, again, oddly enough, said no. The government, still had to find a way to limit what we see and hear; so, through the use of the Federal Communications Commission, it created a loophole so broadcast networks could get around the equal time provision.
Later, in 1987, the two major parties erected another barrier to choices when it comes to electing president of the United States. A bi-partisan effort by the Republican and Democrat parties led to the creation of the Commission on Presidential Debates (CPD). With the goal to provide the "best possible information to viewers and listeners," the CPD (sponsored by some of the largest corporations including Sprint, JP Morgan, Southwest Airlines, and Anheuser Busch) gets the honor of choosing the number of debates that will take place, who will ask the questions, and what questions will be asked for the presidential debates. In other words, it is the two main parties - not we the people - who determine everything about the presidential debates.
The main reason for these constant interventions, of course, is to limit what we see and hear. It's to limit options to the American people, so it makes voting for the lesser of two evils easier to stomach.
Fast forward a few more years. In 1992, independent candidate Ross Perot ran against the two main candidates and was included in the presidential debates. It made sense to include Perot, after all he polled at around 18% of the popular vote. Plus, voters wanted another option; especially after the Iraq war and failing economy (sound familiar?). Indeed, almost 70 million voters tuned in to see and hear the debate (one of the highest watched presidential debates in American history).
Perot's inclusion led to traction for a third party candidate and so the two major parties had to put this to a stop. In 1996, Perot was excluded from the presidential debates as the CPD felt he had no realistic chance of winning. The FEC upheld the exclusion with no explanation (even though the FEC's own general counsel concluded that the CPD violated the law by excluding Perot).
Going one step further - and to justify the exclusion of any third party candidates in the future - the CPD established a rule in 2000, which requires that for any candidate to take part in the presidential debates, he or she must have garnered 15% of voter support in major polls (these polls are conducted by the leading mainstream news that don't often include questions about third party candidates).
And this rule is the justification why only Donald Trump and Hillary Clinton can participate in the 2016 presidential debates. It's not enough that Green Party candidate Jill Stein and Libertarian Party candidate Gary Johnson have consistently garnered almost 15% of American support (at least according to these carefully worded and controlled polls).
But this all makes sense. After all, the two main parties have a major bi-partisan goal: to stay in power. And nothing does this better than limiting what we see and hear.