One of the issues that has kept people from voting 3rd Party is the spoiler effect. To debunk this so-called spoiler effect, Gary Johnson has said that he would draw about the same amount of votes from both parties. Looking at the stats at Real Clear Politics, it appears Gary Johnson is correct. If you compare the polls with Johnson to the polls without Johnson, the net effect to both candidates appears to be a wash.
(change from 2 way race)
And if we add Stein, she does not appear to hurt Hillary’s chances much at all. She takes more votes from Johnson than from Hillary. Oddly, Trump’s percentage goes up when Stein is added. However, the major net affect of including Stein is the reduction of undecided votes.
(change from 2 way race) [change from 3 way race]
It appears most people have their mind made up about Hillary and Trump and only about 20% are willing to consider a third party option even though 47% say they would consider a 3rd party candidate. Despite the fact that more people want to vote 3rd party than the people who support either Trump or Clinton separately, many are still willing to throw their votes away on the major parties instead of rallying behind a 3rd party candidate.
While it may not seem to matter how well a third party will do in the election, there are some ways that it could affect the future of politics. Immediately, receiving 15% in the polls would allow a candidate to be included in the debates. With a four person race, this does not seem like a possibility. Arguably, this should be lowered to 5% or 10% or based on ballot access requirements [i.e. if you are on the ballot in enough states to feasibly win]. If Johnson did garner some more name recognition, he may be able to reach the 15% in the three way race. However, that may prove difficult if they go by the four person race polls.
If a candidate receives 5% of the vote, the party will receive public funding. However, many libertarians do not support this and some, such as Darryl Perry, believe that it may be the death of the LP. However, others have contended that the nomination of Bob Barr marked the death of the LP.
For members of the Libertarian Party [LP], the amount of votes Gary Johnson receives may impact the number of delegates they receive according to the LP by-laws. A state receives a delegate for each 0.35% of the vote for the LP nominee.
For people who care about issues that are ignored by the major parties, they may want to play the long game by supporting a third party candidate. The most realistic affect of 3rd parties is the adoption of issues by major parties that were previously viewed as fringe issues. We can already see this happening. Support for Ron Paul has lead to an increase in the discussion of the Federal Reserve. Being against cannabis legalization appears to be a bad political move now. All of the current candidates for president support some form of cannabis legalization. Even though the election is far from over, third parties are already winning on the issues.