CLEVELAND — Hope springs eternal, especially for third-party presidential candidates. But this time, Libertarian nominee Gary Johnson thinks he has a real shot at making a serious impact in the race for the White House, and if he builds on his current standing he could be right.

Johnson, the former two-term governor of New Mexico, and his vice presidential running mate Bill Weld, the former two-term governor of Massachusetts, argue that they will have a special appeal in the November election because Americans are so unhappy with the major parties and give highly unfavorable ratings to Republican nominee Donald Trump and Democratic candidate Hillary Clinton.

In an interview just outside the perimeter of the GOP national convention in Cleveland Wednesday, Johnson, a soft -spoken, mild-mannered entrepreneur, stayed away from extreme rhetoric. He added that he won't do any negative campaigning – a contrast to both Clinton and Trump, who are eagerly savaging each other.

Johnson does say that Trump's fierce opposition to illegal immigration and his attacks on undocumented workers from Mexico have been "incendiary" in much of the country, including his home state of New Mexico where he says 48 percent of the residents are Hispanic. But he refuses to attack Trump in personal terms. Nor does he get personal in assessing Clinton's much-criticized use of a private email server while she was secretary state. He simply calls it bad judgment. "It's not in my nature to attack," he explains.

He prefers to talk in a wonky way about his policies, pointing out that he supported legalized marijuana before it became accepted nationally. He advocates traditional libertarian ideas such as the need for dramatically less government and lower taxes, and backs a "non-interventionist" foreign policy.

He says it's actually a good time to be an American and that the economy doing rather well but says millions of Americans are upset about "crony capitalism," which he acknowledges is a real problem. "Government is for sale," he says matter-of-factly, without anger or rancor.

His big political objective is to drive his support in national opinion polls above 15 percent, which would earn him a spot in the presidential debates this fall. He drew only 1 percent of the vote nationally as the Libertarian presidential candidate in 2012. He is now polling between 10 and 13 percent in some surveys, and better in a handful of states. He argues that "politics is momentum" and that's what he has right now. But he also knows that third-party candidates tend to fade as voters conclude they don't want to throw their votes away on someone who can't win.