Libertarian presidential candidate Gary Johnson speaks to supporters and delegates at the National Libertarian Party Convention, in Orlando, Fla. on Sunday, May 29, 2016. (AP Photo/John Raoux) File)

If you think the Libertarian and Green Party nominees may have an impact on who wins the White House in November, you need to think again.

They won’t.

As long as Libertarian Gary Johnson and Green Party nominee Jill Stein don’t qualify for the presidential debates, they won’t be able to attract voters away from the two major parties. Only when they can do that will their nominees be in a position to affect presidential contests.

[Why is progressive frustration with Clinton not boosting the Green Party?]

Polls have generally shown the Libertarian ticket of Johnson and Bill Weld, two former GOP governors, drawing from the mid-single digits to the low double-digits. A post-conventions CNN/ORC survey found Johnson getting 9 percent of the vote in a four-way ballot test.

Green Party nominee Stein doesn’t do nearly as well, consistently drawing in the low-single digits. But she did draw 5 percent in the CNN survey.

If both parties receive those levels of support on Election Day, it would constitute a dramatic surge for both of them.

It is also unlikely to happen, though it seems certain that the high negatives of both Hillary Clinton and Donald Trump will boost both the Libertarian and Green Party’s vote totals over 2012.

Johnson was his party’s nominee four years ago, when he drew just under 1.3 million votes – slightly under 1 percent of the total vote – according to election results posted by the Federal Election Commission.

Stein, who recently picked left-wing Ajamu Baraka as her running-mate, also was the Green Party nominee in 2012, when she attracted just under half a million votes – and .36 percent of the total vote.

In other words, the two third party tickets were mere asterisks compared to Democrat Barack Obama’s almost 66 million votes and Republican Mitt Romney’s almost 61 million votes. If the Libertarians and Greens triple or quadruple their numbers from 2012, that would be a noteworthy development.

However well the two third party tickets do, there is no reason – none – to believe they will have a significant impact on the presidential race this year.

Johnson, who will do much better than Stein in November, drew over 2 percent of the vote in four states last time – Alaska (2.5 percent), Montana (2.9 percent), Wyoming (2.1 percent) and New Mexico (3.55 percent), his home state. Stein received as much as 1 percent of the vote in only two states, Maine (1.1 percent) and Oregon (1.1 percent).

Of course, you will hear arguments that neither Johnson nor Stein has to amass a huge vote total to have an impact on the race for the White House.

All they need to do is draw enough votes away from one of the major candidates to “flip” a state, which could change the outcome of the national election. That is what Ralph Nader allegedly did in 2000, according to some Democrats and observers.

But while Clinton and Trump both have plenty of negatives, Johnson and Stein are in no position to steal voters away from them. Voters aren’t really deciding whether to vote for Johnson or Trump, or Stein or Clinton. They are merely deciding whether they can vote for the major party nominees or not.

Those who cannot vote for Trump or Clinton will stay home on Election Day, turn out to vote but skip the presidential contest, or cast their votes for a third party or write-in name.

A vote for Johnson or Stein says one of two things. Either the voter is a Libertarian or Green, or he or she normally votes for one of the major party nominees but finds both nominees this year unacceptable. Either way, Johnson and Stein are not “taking voters away” from the major parties or affecting the results of the November election.

If history is any guide (and it has not always been one this election cycle), support for Johnson and Stein will ebb over the next three months.

Supposedly serious Independent or third party nominees like John Anderson (1980) and Ross Perot (1992) saw their poll numbers slide in the final months of those campaigns as voters decided to cast their votes for someone who could win the White House. That same dynamic could well occur again (Perot’s numbers in 1996 and Nader’s in 2000 remained more stable.)

The Greens probably will attract a handful of Bernie Sanders supporters, but Stein’s (and her party’s) agenda is way too far to the left to attract mainstream supporters who otherwise would support Clinton.

And while Johnson’s decision to add Weld to his ticket surely reflects his effort to move the Libertarians to the political mainstream, that party spends as much time arguing internally about what it stands for as it does wooing general election voters.

As long as the Libertarians and Greens seem irrelevant and outside the political mainstream to the average voter, they will not be in the electoral conversation.

Until that changes, they will remain little more than vehicles of frustration for voters who find one or both of the major parties, and the major party presidential nominees, unacceptable.

Stuart Rothenberg writes about the politics of the presidential and congressional races.