CHICAGO — Union workers at Ford’s assembly plant in Chicago have emphatically voted to reject a national contract that was described as the richest in the automaker’s history, dealing a serious blow to Ford’s hopes of ratifying the deal nationwide.

Production workers with United Auto Workers Local 551 at the plant — Ford’s longest continuously running plant in the world — voted 67 percent against the deal that would have seen them paid $10,000 in bonuses and profit-sharing this year alone. And 78 percent of skilled tradesman at the plant voted against it.

Even before the approximately 4,000 workers in Chicago voted, slightly more than half of the 28,000 who had already voted at other plants around the country had rejected the deal. Ford needs a majority of those who vote among its 52,900 union workers for it to be ratified.

Anger over concessions that longer-standing UAW members were forced to make during the Great Recession, and the high percentage of younger workers who have been hired with lower wages appeared to be behind the Chicago plant’s “no” vote. Workers commenting on the Local 551 Facebook page urged colleagues not to “sell out” to management, who they say have not gone far enough to make workers whole for what they’ve given up over the last nine years.

UAW Local 551 Vice President Scott Houldieson noted that Ford has added two shifts to the Chicago plant since 2010, meaning the plant has “a rather young workforce” compared to some other plants that have backed the deal. But, he said, “There are a lot of longer-term employees that made sacrifices since 2006, so nobody really loved the deal.”

Most workers saw the offer of a one-off $8,500 payment as a bribe, Houldieson said. “That’s one time and it goes away,” he said. “Wage increases are what built the middle class in this country.”

Concerns the deal will be rejected nationwide prompted UAW official Jimmy Settles to warn members before the Chicago result was announced, “When you go back to the table, everything is off the table. So you are negotiating everything all over again.”