Billionaire developer Donald Trump has thrown yet another monkey wrench into the political status quo: Some major labor unions are now mulling endorsing the front-runner for the Republican presidential nomination.

It's a move that would have been unthinkable in previous election cycles, but Trump has fans among the union rank and file and deviates enough from the GOP platform that labor leaders are giving him a serious look.

On Tuesday, the 1.4 million-member International Brotherhood of Teamsters announced its executive council would put off a decision on a presidential endorsement due a lack of consensus. Fox News reported that the delay was caused partly by members' support for Trump and that the union was seeking a meeting with the candidate.

The following day, Chris Shelton, president of the 600,000-member Communication Workers of America, told Politico that his union was putting off a presidential endorsement for the same reason. "If our members come out with Donald Trump, then we're going to endorse Donald Trump," he said.

Getting either unions' support would be a major coup for Trump and a serious problem for the Democratic candidates. The eventual Democratic nominee will need strong support from organized labor in both fundraising and voter mobilization to prevail in the election.

The Trump campaign did not respond to a request for comment.

Representatives for both unions were tight-lipped, but did not dispute the reports of flirtations with Trump, who ranks first in the Washington Examiner's most recent presidential power rankings. However, endorsements from either are by no means assured. Both unions also are considering Democratic candidates Hillary Clinton and Sen. Bernie Sanders, I-Vt., and Trump appears to have done little, if anything, to court labor leaders' support.

Teamsters spokesman Galen Munroe referred to a statement Tuesday by union President James P. Hoffa, which did not mention Trump but did say, "The Teamsters will work with and support any candidate who puts the needs of America's working families above the deep pockets of their corporate donors." Munroe said the union did not have any meetings scheduled with any presidential candidates.

Communication Workers of America spokeswoman Candice Johnson said the union was still polling its members on who to endorse and declined to say exactly how much support had been shown for Trump so far.

"The poll is underway now — it opened in September — and members are continuing to vote into early December, so the numbers are changing. I don't have any further breakdown at this time," she said.

The Teamsters' interest in a GOP candidate is not unprecedented. It has a reputation of being the most conservative among the major unions and endorsed Richard Nixon in 1972. But the communication workers' interest was surprising since it has a much more liberal reputation. The union's immediate past president, Larry Cohen, is a major Sanders supporter.

Roger Stone, a veteran Republican strategist and long-time Trump ally who left his campaign in August after a dispute over political strategy, said the potential support was not surprising. The New York-based developer has a long history of dealing with unions, particularly in the construction industry, and usually finding ways to work with them.

"He's generally union-friendly. He plays golf with and is friendly with, on a social basis, a number of union leaders in New York City," said Stone, the author of The Clintons' War on Women.

Trump was particularly close to Ed Malloy, former president of the Building and Construction Trades Council of Greater New York. Malloy died in 2012.

The union interest in Trump is based more on grassroots support, though, Stone said. The candidate's blue-collar popularism and image as a successful businessman is appealing to regular union members, particularly in the current economy.

"The reason rank-and-file union members are interested is because Trump means jobs. Trump means growth. Trump is a builder. To build that wall in Mexico, that means a lot of jobs," Stone said.

Shelton told Politico that the pressure for Trump was indeed from the grassroots — and he did not sound pleased about it. "Trump is not exactly as pro-union as he seems to be. He deals with unions when he has to. He doesn't when he doesn't."

While Trump has reversed himself on many issues, including immigration, he has a long history of backing unions, at least rhetorically. He told Newsweek in a July interview that he had "great relationships with unions." In his 2000 book The America We Deserve, he wrote, "Is Trump a union man? Let me tell you this: Unions still have a place in American society. In fact, with the globalization craze in full heat, unions are about the only force reminding us to remember the American family."

Trump is a card-carrying union member himself, having joined the Screen Actors Guild as a result of his numerous appearances in television and in movies.

Trade is one of the main areas of common ground between Trump and the labor movement. Like them, he is a major critic of President Obama's trade agenda, including the 12 nation Trans-Pacific Partnership trade deal, which is expected to go before Congress early next year. Trump has argued Obama is giving away too much in the negotiations.

Most union leaders favor pro-immigration reform efforts, but there is considerable internal dispute on the issue, with many opposing worker visa programs as costing jobs. It took the AFL-CIO labor federation several months of negotiations with the Chamber of Commerce in 2013 before they could unite behind even a vaguely worded common immigration reform plan. Trump's staunch opposition to immigration presumably appeals to many of those disaffected grassroot members.

It is not clear where Trump stands on several other issues related to unions such as "card check" election reforms to make workplace organizing easier, right-to-work laws that prevent workers from being forced to support unions as a condition of employment or the Obama administration's efforts to expand the definition of a "joint employer," making corporations legally responsible for labor law violations by subcontractors and franchisees.

Liberal critics point out that his support for unions do not necessarily extend to his own businesses. He has resisted efforts by the service workers union Unite Here to organize the Trump International Hotel in Las Vegas.

Getting more than token organized labor support would require Trump to address those issues in his campaign, something he has shown little interest in so far.