Image copyright Getty Images Image caption Gary Johnson says his Libertarian party is a natural home for conservatives disaffected by Trump

Libertarian Gary Johnson believes this could be the year his party, a perennial non-contender in US presidential elections, shakes up the campaign in a way it has failed to accomplish in past cycles. Andrew Desiderio reports on his chances.

Republicans and Democrats. Democrats and Republicans. Thus it has been, thus it will always be. Or could 2016 - a year of eye-popping firsts in presidential politics - be different? Could it be the moment the Libertarian Party steps into the spotlight?

Mr Johnson, the former two-term Republican governor of New Mexico who appears poised to once again be the Libertarian standard-bearer, certainly thinks so. He views his party as the natural home for Republicans recoiling from the prospect of Donald Trump as their nominee.

"If they're honest with themselves and they really are about smaller government, then I'm it," Mr Johnson said in a recent interview with the BBC in Washington.

There is some evidence to back up Mr Johnson's hopes. Mr Trump has eye-popping unfavourably among female voters, minority groups and even the most conservative Republicans.

An exit poll from the 15 March primaries showed that 61% of GOP voters who did not cast their ballots for Mr Trump would seriously consider a third-party alternative to Mr Trump and Hillary Clinton, the presumptive Democratic party nominee.

All this has sparked talk of other options for disaffected Republicans - but the choices are limited. State filing deadlines for an independent conservative candidate to get on the ballot are rapidly approaching.

Image copyright Getty Images Image caption Thirty party candidates debate in 2012

The Constitution Party, which has limited reach, has its nominating convention in early April. The Green Party? Not exactly a friendly home for conservatives.

Then there's the Libertarian Party, which tends to attract Republicans who are more socially liberal, and is likely to have their nominee on the ballot in all 50 states this year. Johnson's presence could help Republicans avoid disastrous down-ballot consequences in pivotal House and Senate races, which could be compromised if Republicans are not enthused enough by Trump to show up to the polls.

Prominent Republicans such as 2012 presidential nominee Mitt Romney and Nebraska Senator Ben Sasse have suggested they would choose a third party candidate if they were faced with the choice of Mr Trump or Mrs Clinton.

Mr Johnson believes Mr Romney and Mr Sasse are implicitly suggesting he is that candidate.

"They're not saying Gary Johnson, but they know that it's the Libertarian Party," he predicted. "They haven't said it. They know that the leading contender for that nomination is Gary Johnson, and they're not saying that either."

Fiscal conservatism and social liberalism are the Libertarian party's hallmarks, and Johnson believes that many Republicans - especially young conservatives and those who despise Trump - are at least "socially tolerant".

"Talk about setting the table for the Libertarian nominee - this is it," Mr Johnson said. "If people collectively don't have a head jerk and ask, 'Well, what's the other alternative?' I don't know if they ever will."

Image copyright Getty Images Image caption Bob Barr ran for president as the Libertarian candidate in 2008 - and received 0.4% of the popular vote.

Mr Johnson, who briefly ran for the Republican presidential nomination in 2012 before becoming the Libertarian candidate and garnering just 1% of the popular vote, understands the Trump phenomenon and the real anger that voters have.

When he first ran for governor in 1994, Mr Johnson made a similar pitch to New Mexicans that Mr Trump is currently making to the country - a political outsider who built a successful company and wants to apply those business principles to government. But that is where the parallels end.

"I never said anything as crazy," as Mr Trump's proposals on immigration and foreign policy, he added. "To me, it alienates more than half of Republicans."

Mr Johnson has repeatedly said in recent years that most Americans are Libertarians - but they "just don't know it". He even believes that the party would rake in millions of dollars if voters perceived the Libertarian nominee to be a competitive candidate.

The key to that viability, however, is visibility - and there's no bigger stage than the general election debates. The Commission on Presidential Debates has determined that in order to qualify, a candidate must reach at least 15% in an average of five recent national polls - a threshold the Libertarian candidate has never met.

A recent Monmouth University poll, however, offered a ray of hope - putting Mr Johnson at 11% nationally in a hypothetical three-way race with Mr Trump and Mrs Clinton.

Image copyright Getty Images Image caption Jill Stein is running for president through the Green Party - but its unlikely anti-Trump Republicans will land there

The national party has filed a lawsuit against the commission in conjunction with the Green Party, alleging that the 15% rule is not legal on anti-trust grounds.

Mr Johnson argues that if a candidate is on the ballot in all 50 states and therefore has at least the mathematical possibility of winning 270 electoral votes, he or she should be allowed on the debate stage.

Kyle Kondik, an elections analyst at the University of Virginia Center for Politics, told the BBC he could envision a candidate such as Johnson receiving a "significant number of protest votes - probably not enough to win a state, but just enough to deprive Trump of votes in certain places".

"The opportunity is there for Johnson if there is no other third party Republican or third party conservative, maybe he gets more attention and more votes," he added,

Media attention on Mr Johnson has been scant so far, despite the deep dissatisfaction that voters have with the two presumptive nominees.

Regardless of the scepticism surrounding his chances, Mr Johnson does not worry about what's next for him or the political process he seeks to revolutionise.

"If at the end of the day it ends up to be whatever it ends up to be, I sleep at night because I was the voice of reason in the whole process," he said.