But the former Republican New Mexico governor argues he could win the White House in November if he can break the 15 percent threshold in national polling in the next four weeks and get on stage at the first presidential debate on Sept. 26.
"If we're in that presidential debate, I think, anything is possible. And given the momentum that we have, I think it's possible that I will be the next president," Johnson said in an interview this week. "I know that just sounds crazy, but we would not be doing this if we didn't think that ... that possibility exists."
The Libertarian's bold prediction comes as his standing in state and national polls has risen this summer and voter consternation has resulted in historically low popularity ratings for Democrat Hillary Clinton and Republican Donald Trump. In an average of recent national polls, Real Clear Politics showed Johnson with about 9 percent support.
Johnson sees an opportunity in Michigan. He is scheduled to address the Detroit Economic Club at the Westin Book Cadillac hotel on Sept. 14, the club announced Thursday, but the subject of his speech isn't known.
In Michigan, Johnson captured 7.5 percent of support among 600 likely voters in a July 30-Aug. 1 statewide poll commissioned by The Detroit News and WDIV-TV. The inclusion of Johnson and Green Party candidate Jill Stein in the poll cut into the margins of both the GOP and Democratic nominees — a 5 percentage-point loss for Trump and 2.5 percentage-point drop for Clinton.
Johnson's support topped 10 percent in the Republican stronghold of West Michigan and 16 percent among likely voters in Livingston, Monroe, St. Clair and Washtenaw counties, according to the poll. The survey had a margin of error of plus-minus 4 percentage points, but the error margin rises in regional comparisons because of smaller voter samples.
The backing for Johnson helped give Clinton a narrow lead in west Michigan, where the Republican nominee would traditionally be on solid ground, said pollster Richard Czuba of the Glengariff Group Inc.
"If I were the Clinton campaign, I'd be buying Gary Johnson a plane ticket to Grand Rapids," Czuba said.
Tiffany Hayden, the Libertarian candidate in the 13th Congressional District, said Johnson offers a credible alternative to voters who feel resigned to picking between Trump or Clinton.
"Trump or Hillary? I find them both horrifying, and I think a lot of other people do also," said Hayden of Garden City. "When they say vote for the lesser evil, some people don't want to vote for evil. And I think people can vote for Gary Johnson with a clear conscience."
'Vetted by own experience'
Michigan Libertarians are energized about Johnson and vice presidential nominee Bill Weld, a former Republican who was governor of Massachusetts from 1991 to 1997. Johnson, who was New Mexico's GOP governor from 1995 to 2003, and Weld both got re-elected in Democratic-leaning or solid Democratic states.
"I think that removes any of the kook factor — the concern that somebody from a fringe party ... would somehow be viewed as maybe not reliable, or unsafe," said Scotty Boman, a perennial Libertarian candidate from Detroit who is state director of the Johnson-Weld campaign. "They've both been vetted by their own experience."
Johnson espouses replacing the federal income tax with a sales tax, ending American pursuit of "regime change" in war-torn Third World countries, legalizing marijuana and getting the government out of the business of deciding who can marry whom.
Johnson also has said he believes climate change is man-made and supports leveling polluters with a carbon "fee" — a proposal that has drawn sharp criticism from libertarian commentators as a euphemism for a tax and at odds with their ideology.
"Starting with philosophy, I think we represent the majority of Americans," Johnson said Tuesday in a conference call with The Detroit News and two other regional news outlets.
Johnson and Weld also are actively promoting international trade agreements in stark contrast to Trump and Clinton, who have vowed to oppose the 12-nation Trans Pacific Partnership pact involving many Pacific Rim nations as well as the United States, Canada and Mexico.
"We're the free-trade candidates here and we do support TPP," Johnson said. "We think it really does expand free trade."
Debate remains long shot
Like any third-party presidential campaign in modern U.S. history, Johnson faces long-shot odds of getting on the same debate stage with Trump and Clinton next month at Hofstra University in New York, much less winning the 270 electoral votes needed to capture the presidency.
The last third-party candidate involved in presidential debates was the Reform Party's Ross Perot, the Texas billionaire who qualified for the three debates, including one at Michigan State University.
The problem for Johnson is that just 4 in 10 Michigan voters surveyed by Glengariff Group could identify him by name.
The Libertarian candidate's strongest support in the recent Detroit News/WDIV poll came from college-educated men who vote Republican or consider themselves political independents, Czuba said.
"It's kind of the Justin Amash voters, people who do tend to lean libertarian a little bit ... who are seeing him as the option instead of voting for Trump," said Czuba, referring to the maverick Republican U.S. Rep. Justin Amash from Kent County.
Johnson could find inroads with GOP women, 1 in 5 of whom were undecided in the recent poll, Czuba said.
"Republican women are pretty ripe for picking for right now," he said.
Johnson was the Libertarian Party presidential nominee in 2012, but missed the deadline that year to get on the ballot in Michigan. He received 7,774 write-in votes, 2,627 more votes than the Natural Law Party nominee, Ross C. Anderson, whose name was on the 2012 Michigan ballot.
This week, Johnson gained access to the ballots in Ohio and Alabama, and his name will be on the ballot in at least 42 other states and the District of Columbia, said Carla Howell, political director for the Libertarian Party.
"I think we're going to surprise in a big way," Johnson said. "I think America loves an underdog, and we're clearly an underdog here."
Trump, Clinton criticized
As Johnson tries to boost his standing and name identification, he has been sharpening his criticism of Trump and Clinton.
"For Hillary Clinton, I think everything is about growing government, that taxes will go up," he said.
Clinton's work as secretary of state caused the Middle East to become more destabilized, Johnson said, giving rise to the Islamic State terror group.
"In Syria and Iraq, it's resulted in empowering ISIS," Johnson said. "And that's not intentional, but that is what has happened."
On Trump, the peace-promoting presidential candidate criticized the New York billionaire for advocating the use of "water boarding, torture or worse" to extract intelligence from America's enemies.
In questioning Trump's recent attempt to express regret for some of his campaign rhetoric, Johnson said the Republican nominee has been less than truthful with the public.
"I do have this philosophy that if you tell the truth, you don't have to remember anything," he said. "And if you tell the truth, that means you will admit mistakes."