After decisively winning three out of the five Republican presidential primaries on March 15, the likelihood of Donald Trump becoming the 2016 GOP nominee is looking more probable than ever. However, an anti-Trump movement has been growing within the Republican Party, prompting Mitt Romney to speak out against the front-runner, several PACs to air ads attacking his character, and hashtags like #NeverTrump and #MakeDonaldDrumfAgain to trend on Twitter.

Is it likely then that anti-Trump Republicans will either vote Democratic or not vote at all should he secure the nomination?

A recent USA Today/Rock the Vote poll shows that millennials overwhelmingly do not like Trump. In fact, the poll even suggests that Donald Trump could be the “way for Hillary Clinton to solve her generation gap,” noting that while Clinton is still losing to her opponent Bernie Sanders amongst millennials, numbers show that voters under 35 would choose her over Trump in the general election by 52 percent to 19 percent.

To add fuel to the fire, a campaign ad from 1964 entitled Confessions of a Republican recently resurfaced on Facebook, and it draws striking similarities to the current 2016 political climate.

“I certainly don’t feel guilty about being a Republican. I’ve always been a Republican,” says a man in the ad. “But when it comes to Senator Goldwater, now it seems to me we’re up against a very different kind of man. This man scares me.”

The man in the ad speaks about his past voting record and his dismay regarding the 1964 Republican presidential nominee.

“I wouldn’t have worried so much about party unity because if you unite behind a man you don’t believe in, it’s a lie,” he continues. “When the head of the Klu Klux Klan, when all these weird groups, come out in favor of the candidate of my party, either they’re not Republicans or I’m not.”

The ad, which ends with the words “Vote for President Johnson on November 3,” has surely reappeared with the intention of convincing Republicans to vote for the Democratic nominee instead of Trump. However, just as there was a Johnson running in 1964, there is another Johnson running today in 2016.

“2016 could be the year when the two-party hold on American elections falls apart -- and it’s about time,” wrote Libertarian candidate Gary Johnson, in a response to last night's primary results. “Exit polls from Tuesday show that fully one-third of Republicans will consider a third-party candidate if Trump and Clinton are the nominees in November. On the Democrat side, it is difficult to imagine voters who are energized for Bernie Sanders taking that enthusiasm to Hillary Clinton.”

Voting against Trump in the general election doesn’t necessarily have to mean voting for a Democrat, but would Republicans actually consider a third-party candidate? Young Republicans might.

A recent article by The American Conservative, titled No Party Owns Us, suggests that young voters “prioritize principles over party, ideas over ideology.” Over half of all millennials consider themselves independents, and even a large number of those who consider themselves conservatives are libertarian-leaning or moderate.

“I would submit that the true ‘mainstream’ in American politics today, especially among the critical 80 million millennials who comprise the largest voter segment in U.S. history, adheres to the simple idea that government is too big, costs too much, and has in fact become a corrupt threat to individual freedom,“ continues Johnson’s response. “Both the Republican and Democratic parties have fumbled around and constructed nomination processes that make it virtually impossible for a candidate reflecting that ‘mainstream’ to emerge. The American people see that, and it’s time for the real majority to stand up and try something different.”

Perhaps they will.