"This is not about unions. It's about working people," Josh Windy of the Plumbers and Pipe Fitters Local 85 of Saginaw told the Detroit Free Press. "He's giving money to businesses and taking money from working people."
The newspaper estimated the crowd at 3,000 to 4,000. Michigan-born filmmaker Michael Moore had called for a large turnout.
Leaders of the Legislature's Democrats said they will propose a constitutional amendment to protect collective bargaining rights, The Detroit News reported.
"In the midst of … other Republican-led, union-busting efforts, they will be introducing an amendment to protect collective bargaining rights," spokesman Alex Rossman said.
Legislation enabling "emergency financial managers" passed the state House Tuesday and is headed to Snyder for his signature. Another 40 bills introduced since January would roll back bargaining rights, opponents say.
Snyder, at an unrelated news conference elsewhere, said the protest is "part of the democratic process. I just hope people will always be respectful."
On Tuesday, more than 1,000 senior citizens rallied at the Capitol to protest Snyder's plan to tax pensions.