The two major party nominees are the most unpopular in modern American political history.  The Libertarian Party has been around a long time, and its nominee, former governor Gary Johnson of New Mexico, has a pleasant and reasonable demeanor as well as positions on issues that are consistent and clear (whether one agrees with the Libertarian position or not).

Johnson and his running mate, former Massachusetts governor William Weld, have both shown the ability to win twice in gubernatorial elections as Republicans in blue states.  Although the positions these two men have on some issues, like legalizing drugs, is unpalatable to many social conservatives, both are honest about their positions, and both have reputations as honorable men.   

One of the principal objections Libertarians have had to face in past elections is that voting for the Libertarian nominee is effectively voting for the Democrat, because the Libertarian cannot win.  If it begins to look impossible for Trump to win, however, Gary Johnson, a likeable, honest, intelligent former Republican, may look better and better.  But Johnson has to get his message out to the voters on an equal stage with Hillary and Trump, which requires reaching that magic threshold of 15% of the average in presidential polling before the first debate.

Through mid-August, Johnson is averaging 8.4%, which would seem to be far below that threshold.  But there is something different about the two major party nominees this election cycle: the vast majority of the voters don't much like either one, and the percentage of voters who decline to support either one is very high.

The RCP average as of August 16 shows that the combined percentage of respondent support for Hillary and Trump is 80.2% in those polls.  Most August polls showed the combined percentage of support for both of the two major party candidates in the seventies – Reuters (74% and 75%), The Economist (76% and 78%), Breitbart (79%), IBD (74%), Marist (76%), and The Wall Street Journal (77%) – which is particularly dreadful for two candidates already nominated and who have been in the public eye forever.

That suggests that between 20% and 25% of Americans reject both Hillary and Trump, and although 3% consistently support the Green Party, the remaining 17% to 22% is more than enough to get Johnson into the debates.  What might happen then?  The debates might make Johnson a viable candidate.

It is impossible to portray Johnson as an "insider" or an "Establishment Republican."  Gary Johnson is, instead, the former governor of a middle-sized state far from the Beltway.  Johnson left the Republican Party but declined to join the Democratic Party because these he sees Democrats as at least as bad as Republicans.

Gary Johnson might well flop in the debates – he is hardly a dynamic speaker – but he might also seriously present himself as the only real alternative to that two-party Washington-centered system that today revolts and repels so many Americans, especially those in Flyover Country.  If in the first debate Johnson were able to present that image credibly, then anything might happen.

This election ought to be clear evidence that the old rules don't apply any more, as Trump and Sanders showed. 

Could Johnson win?  That rather depends upon what happens to the Trump campaign.  Hillary is the ultimate Washington insider and the heir to Barry's mess.  Trump ought to have been able to put her away by being a credible alternative to the dismal prospect of a Hillary White House, but Trump seems a much worse general election candidate than Republican nomination candidate. 

If Trump recovers from his missteps and becomes competitive, then Johnson will have a bar to his maximum support of around 20%, rather like Ross Perot in 1992.  But if the Trump campaign continues to unravel, then all of those Americans who loathe Hillary, which is to say a strong majority of Americans, may see this Gary Johnson, who is calm and good-natured and who has actually run a state and stood up for his principles as a governor, as the best choice to beat Hillary.

The vast and disillusioned Republican base across America that distrusts Trump may see Johnson as a credible candidate for the White House.  Stranger things have happened.  Indeed, stranger things have happened this election season.