If you want a more representative government, a third party is the wrong solution.
Many believe that the United States is becoming more polarized, as Americans increasingly flee the political center in favor of partisan ends of the ideological spectrum. This is not a consensus view, and there are compelling arguments to the contrary. Nonetheless, a similar trend that is beyond dispute is that Americans have grown dissatisfied with the two major political parties. To resolve their dissatisfaction, many Americans yearn for a third party that would better represent their interests. This desire is understandable and well intentioned, but a viable third party is the wrong anecdote to our political woes. In fact, given the way the American political system functions, a viable third party would likely make things worse.
The inconvenient truth is that our political system does not create incentives for bipartisan cooperation. From an electoral perspective, congressional races are mostly not competitive in the general election, because the partisan weight of most districts is too stark. This means that most Members of Congress have more to fear from ideological hard-liners in their own party than from partisan opponents. Compounding the problem is the fact that voter turnout in primaries and caucuses, which determine who will represent each party on the general election ballot, is extremely low. Those who do come out and vote are typically hard-liners who are least likely to tolerate bipartisan tendencies in a nominee. This minuscule percentage of American voters controls our political system.
In most competitive congressional districts today, one Republican and one Democrat compete for the most total votes, but neither needs to earn the most votes overall to win the election. With write-in's, non-votes, and small party candidates on the ballot, candidates can easily win election with less than a majority of votes. In many cases, third party candidates would exacerbate this problem by handing political power to even smaller pluralities of voters. A viable third party with a large voting constituency would likely cause winning pluralities to shrink, perhaps as low as around 40 percent. This would be counterproductive if your goal is to make the American government more representative of its citizens.
Once in office, political parties face few procedural incentives to cooperate across party lines. Congressional norms, especially the Hastert Rule, ensure that hardliners' policy priorities receive greater attention than more popular issues. This is partially why the Republican Party in 2017 has prioritized corporate tax cuts and revoking low-income Americans' access to healthcare over more popular policies, such as infrastructure investments. The unfortunate truth is that the only way to bring about dramatic reforms in the U.S. today is to win partisan majorities in the House of Representatives and Senate (ideally, 60+ senators), while that majority simultaneously occupies the presidency. Otherwise, it is easy for minorities of legislators to place constitutional and procedural wrenches into the gears of the federal government.
If you introduce a third party into Congress, there is no clear path to electing the Speaker of the House and, by extension, determining the federal legislative agenda. If no party could command a majority, Members would need to strike a deal that would pool support from multiple parties. This is normal in parliamentary systems, but the American system is not equipped for it. The smaller party in this hypothetical deal would have less leverage than is typical in parliamentary systems, where junior coalition partners can topple governments and force new elections. Their only real leverage would be to force out the Speaker. That is significant, but I'd argue insufficient to ensure that the coalition remains healthy. There is simply no way to ensure that the smaller party's priorities receive adequate attention.
There are real reforms out there that would better address Americans' dissatisfaction with their government. I may write about those at another time, but am particularly sympathetic to proportional representation. In the meantime, we should stop looking to the likes of Gary Johnson and Jill Stein in hopes of finding a solution. They aren't going to lead us to a more representative government, but they could give us a worse one if we aren't careful.