(CNN) With the Republican presidential nomination within his grasp, Donald Trump is courting an unlikely group of voters: Bernie Sanders supporters.

The GOP front-runner has ratcheted up his rhetoric against presumptive Democratic nominee Hillary Clinton in recent weeks, calling her a "crooked" politician who is unqualified to be president. But when it comes to her challenger, Bernie Sanders, Trump has taken a notably softer tone, praising the Vermont senator's rhetoric and encouraging him to launch a third-party bid.

"I think Bernie Sanders should run as an independent. I think he'd do great," Trump said at a victory rally in New York City Tuesday night, after sweeping five GOP contests in the Northeast.

The next morning, Trump said on MSNBC: "Bernie Sanders has a message that's interesting. I'm going to be taking a lot of the things Bernie said and using them."

Trump's advisers say these comments are a preview of more explicit overtures the campaign is ready to make to Sanders' supporters once the populist liberal exits the 2016 race. That strategy is based on the broad areas of overlap between voters attracted to Trump and those who have flocked to Sanders. Both have angrily denounced the political system as corrupt and expressed deep frustration that Washington is not helping ordinary people. They both oppose international trade deals, saying they hurt American jobs.

And, of course, targeting Sanders supporters could serve to undermine Clinton.

Trump campaign manager Corey Lewandowski said the campaign is ready to bring into the fold anyone in the "feel the Bern" movement who is not inclined to support Clinton in the general election.

"You have two candidates in Donald Trump and Bernie Sanders which have reignited a group of people who have been disenfranchised and disappointed with the way Washington, D.C. and career politicians have run the country," Lewandowski said. "Bernie Sanders has large crowds — not as large as Mr. Trump's, but large crowds — and so there is a level of excitement there for people about his messaging and we will bring those people in."

But even as the two candidates share similar campaign messages, there is a big hurdle to Trump winning over Sanders supporters. A recent Washington Post/ABC News poll showed that among Democratic leaning voters who want Sanders to be the party's nominee, only 13% of them view Trump favorably, while 86% view him unfavorably.

And Sanders has been unequivocal: he wants the eventual Democratic nominee to defeat the Republican.

Still, Trump and Sanders have both caught party leaders by surprise this year with the size and intensity of their followings.

Trump is a brash Manhattanite who runs a multi-billion dollar real estate empire and has never sought public office; Sanders was born in Brooklyn and has been in public office since the 1980s, advocating for progressive causes like raising the minimum wage and affordable housing.

Despite their starkly different backgrounds, both Trump and Sanders have managed to garner huge followings by tapping into a similar anger that's erupted into the open in this election cycle. Trump, even as he frequently boasts about his personal wealth, has made a point of disavowing special interests and corporate money like Sanders, billing himself the only candidate that is "self-funding" his presidential campaign. On the stump, the two men both passionately rail against a political system that is designed to prop up the elite while ignoring lower- and middle-class Americans.

Marina Coddaire, a 25-year-old woman from Woodbury, Connecticut, is a registered Democrat who is supporting Sanders. But over the weekend, she was in the audience of a Trump rally in Waterbury. It was "curiosity" that brought her there, she told CNN: "I just want to see it for myself."

"I feel that the core of both what Bernie's movement is and Trump's movement is, is the same. This anti-establishment, being upset with the way that our government has been run and how the mistakes that they've made have really damaged the middle class and have disenfranchised them," Coddaire said. "This cry of change. The way that they've both gone about it is of course different but I still respect it."

Coddaire said she would not vote for Clinton in the general election but left the door open — just a crack — to the possibility of supporting Trump in November.

"I really, really, really do not want to vote for Hillary Clinton," she said. "So when the media says... oh no, they'll make the switch, they'll consolidate, I don't think they will. Because I'm not going to."

Other Sanders fans are far less willing to consider Trump as an alternative.

At a Sanders rally at Purdue University in Indiana on Wednesday, one Sanders supporter said he would "never even consider" supporting the New York billionaire.

"Trump's hurdle is, you can't believe anything he says," said David Mason, a 42-year-old Lafayette photographer. "Yes, he and Bernie have some overlap on issues. But as people, they couldn't be more different."

Bill Hillsman, a political consultant who has advised many independent candidates, said not only is there real potential for Trump to grow his base by reaching out to Sanders fans, it is crucial that Trump win over independents if he wants to win the general election.

"It's evident many Democrats (and certainly those supporting Bernie) find Hillary's campaign lacking," Hillsman said. "So what Trump is doing is smart. The only possible route to a November win for him is on the backs of independent voters."