In the spring of 1775, just weeks after the bloody skirmishes outside Boston that mark the beginning of the American Revolution, a gang of angry New York City patriots stormed the home of an early president of King’s College, now Columbia University. The mob had been stirred up over a series of days by fiery public speeches, overheated pamphlets, and alcohol, and was zeroing in on the outspoken Tory, Myles Cooper, with designs on his life. They were out for blood.

Luckily for Cooper, the mob’s progress was halted by one of his students. Alexander Hamilton, a young patriot who had helped incite the mob, had suddenly grown fearful of its strength. Hamilton turned the crowd away in an early instance of the ambivalence he would show throughout his life toward mobs. As a biographer of the future treasury secretary, Ron Chernow, writes: “The episode captured the contradictory impulses struggling inside this complex young man, a committed revolutionary with a profound dread that popular sentiment would boil over into dangerous excess.”

A mob of similar proportions made noise at the state Capitol last month, emboldened by the rhetoric of another sometime populist of Manhattan. Just one day after burying the union-backed West Side Stadium, the speaker of the Assembly, Sheldon Silver, rose before roughly 1,000 members of the Public Employees Federation to pledge his support for legislation aimed at establishing greater oversight in selecting private contractors for public projects. The 52,000-member union pushed four bills connected with outsourcing this session. One is making its way to Governor Pataki’s desk.

The origin of the rally, and others like it in New York City and Albany in recent weeks, is a five-year-old audit of the Department of Transportation by the accounting firm KPMG, which said private consultants cost the state 75% more than in-house staff. The report was a boon to union organizers, who have used it ever since in countering arguments that the state saves money by outsourcing jobs. A recent report by the union-backed Fiscal Policy Institute said New York would actually save up to $500 million annually by increasing its public workforce.

Naturally, private contractors dispute these claims. They say the state saves money by not paying for the latest technology or for the advanced training that private consultants bring to the job. They say private workers who are not constrained by union rules on overtime finish projects more quickly than state workers. And they argue that studies like the one published by the Fiscal Policy Institute neglect to factor in pension costs and vacation time. “It’s a very selective comparison,” a lobbyist for The American Council of Engineering Companies of New York, Chris McGrath, said.

In cooler moments, both sides in the debate over the use of private consultants for public projects acknowledge their mutual dependence. Private professionals earn billions from state contracts annually even as the state leans on private designers and other specialists to ensure that expert work is done in a timely manner. “Both entities have a very important role to play,” Mr. McGrath said. “One should not be denigrating the other.” A spokeswoman for the public employees union, Darcy Wells, agreed, downplaying the impact of the four bills that circulated this year. “It’s really just about transparency,” Ms.Wells said, “and putting everything on the table.”

Still, the lengths to which unions have gone to promote mere transparency suggests that something more here is at play. The three recent rallies in Albany and New York City were only a piece of the union’s mobilization efforts this year. In the final weeks of the session, PEF ran television commercials caricaturing businessmen that would have made Thomas Nast blush. By depicting a faceless man chortling in a suit while hording dollar bills, the ads were aimed not so much at promoting the idea of transparency as they were at dramatizing the supposed rapacity of private interests.

Indeed, if three of the accountability bills proposed this year are largely redundant, as Mr. McGrath said, and would have a benign effect on the regulatory landscape (the fourth bill, which has no chance of passage this year, is more prohibitive than regulatory), then why the foment? One possible answer is that unions, not unlike like political parties, accumulate and retain power by appealing to a base: Without a strong message, rallies won’t be charged; without a show of force, legislators won’t listen when the legislation really counts.

Whether Mr. Pataki goes along with efforts to squeeze private contractors by trading in his purported limited government principles for political support from unions next year remains to be seen. He has done it before, and speculation that he is considering another run next year could make such a move even more likely. A more important group to watch, however, will be the Legislature, where Mr. Silver and the majority leader of the Senate, Joseph Bruno, have more openly and consistently depended on the support of unions for votes. Until then, all three groups could learn a lesson from Alexander Hamilton on the proper balance between respect and fear for the mob.

Mr. McGuire is The New York Sun’s Albany correspondent.