Days after reaching an agreement with Uber and Lyft requiring the companies to increase wages and benefits for their drivers, Massachusetts Attorney General Andrea Campbell supported a separate initiative to allow those drivers to unionize.

Campbell on Tuesday endorsed a union-backed ballot proposal that would allow on-demand transportation drivers to organize and bargain collectively, calling it an important addition to terms her office had already negotiated.

“Our agreement with Uber and Lyft secured an unprecedented package of minimum wage, benefits and protections for workers. It is a strong foundation that can and should be built upon,” Campbell said in a statement from the Drivers Demand Justice Coalition. “I am proud to support this ballot question, which, if passed, would give workers the ability to collectively bargain for even higher wages and benefits.”

The agreement between Campbell's office and Uber and Lyft, unveiled Thursday, requires the companies to pay drivers at least $32.50 an hour for the time between accepting a ride and dropping off a passenger. It also provides paid sick leave, workers' compensation and access to health benefits. The companies will also pay $175 million, most of which will be earmarked as compensation for drivers.

The Massachusetts Attorney General's Office announced a settlement with two rideshare giants.

Uber, Lyft, DoorDash and Instacart had for years pursued their own ballot proposal that would define drivers as independent contractors rather than employees, but they ended their campaign in the wake of the deal. Now the union measure will be the only app-based driver issue voters will decide this fall.

Organizers plan to submit the final batch of signatures later in the day to secure a spot on the Nov. 5 ballot.