As a Republican presidential nomination for Donald Trump becomes more probable, some liberals are warning their colleagues that he could revive the "Reagan Democrat" phenomenon by getting support from blue-collar voters who don't automatically back the GOP. That coalition was widely seen as crucial to Reagan's victories, and its return could cause serious trouble for a Democratic candidate's prospects in 2016.

Asked Friday by Fox which Republican candidate presented the biggest threat to the eventual Democratic nominee, former Rep. Dennis Kucinich, D-Ohio, said without hesitation that it was the billionaire developer and former reality television star.

"Donald Trump has appeal with the old Reagan Democrats. There's a new generation of them and Donald Trump, from my experience, seems to be reaching them ... He has a broader bandwidth than any other candidate," said Kucinich, former chairman of the House Progressive Caucus.

In an email to the Washington Examiner, Kucinich elaborated that Trump was stirring up an "amorphous spirit of revolt" that has been building for a long time among blue collar voters. "He is not only his own man, he is his own ideology, transforming complexities to simplicities, welcoming masses to participate in the magical thinking of certainty propelled by his powerful will," he said.

A survey of white blue-collar voters in Cleveland and Pittsburgh neighborhoods released Thursday by Working America, a nonprofit affiliate of the AFL-CIO, the nation's largest labor federation, found that Trump was the top choice of a third of the 1,689 people surveyed. Even one-quarter of the people who identified as Democrats said they were leaning towards him. Overall, the group leaned Republican, 41 percent, while 32 percent identified as Democrats and another 27 percent as independents.

"Canvass organizers were struck by the level of emotion expressed by voters, both in describing their own (economic) circumstances and stresses, and in their feelings about some of the candidates, especially among those who ardently supported Trump. One-third of Trump's supporters said they weren't considering anyone but him," the study found.

One possible reason for the appeal is that while Trump is best known for his opposition to immigration, he has also bucked Republican free market orthodoxy on number of economic issues by adopting more populist positions. He has criticized free trade deals, attacked big business for outsourcing jobs and moving companies oversees, and endorsed higher taxes on the wealthiest people, at least rhetorically. His official proposed tax reform package doesn't do this, and opposed reducing the size of government or reforming entitlements. That gives him an opening to appeal to economically-stressed Democrats.

Working America said that while immigration was a contributing factor to Trump's success with these voters, it was the top issue of only five percent of the people surveyed overall. Even among those who were supporting Trump, it was only the third-most important issue, with the economy and the terrorism coming before it.

"[A] far greater number of prospective voters are more deeply concerned about the economy and about their fates, and the future of their families, in a time of rapid change," the survey found. "White working-class voters often feel powerless to change a government that they do not see as respecting their concerns or serving their needs."

Former Rep. Steve LaTourette, R-Ohio, said he has seen the strength of Trump's appeal in his old district, which includes suburbs of Cleveland, Akron and Youngstown. "I used to represent a lot of Ford Motor plants in a heavily unionized district ... If you think about Trump's anti-immigration message, well, who gets replaced?" LaTourette said, adding that the billionaire's "Make America great again" slogan has an automatic appeal to these voters.

LaTourette said some of these people are just culturally conservative to start with. "You'll see a lot more National Rifle Association signs than you will United Auto Worker ones," he said.

Matt Morrison, deputy director of Working America, said the biggest takeaway from his group's study is that most of the people surveyed were not firm on who they'll support for president. "One of the things that we found was that just a little bit of new information alters what they thought they knew about Trump."