The California Federation of Teachers and the Courage Campaign are among the groups backing the proposed ballot initiative to raise income taxes on people who make more than $1 million a year.
Supporters expect to raise the $2 million they will need to get the initiative on this year's general election ballot, then another $8 million to $10 million for the campaign.
"We're the one measure that doesn't put an additional burden on the back of middle-class and working-class families," campaign chairman Anthony Thigpen said during a conference call with reporters.
The proposal also is supported by the California Nurses Association, one of the state's most powerful interest groups.
It is one of three tax increase campaigns planned for the November ballot, each of which has influential supporters that have been politically aligned in the past.
Brown has warned that a ballot containing too many similar-sounding tax initiatives could confuse voters and jeopardize success.
The Democratic governor has raised nearly $2.2 million for his own proposal, which would temporarily raise income tax rates on those who make more than $250,000 a year, and increase the state sales tax by half a cent. The California Federation of Teachers and other groups oppose the broad-based sales tax increase, which they said affects those who can least afford to pay more.
The third initiative is being promoted by wealthy Los Angeles attorney Molly Munger. It would raise income taxes on a sliding scale to boost funding for public schools.
Munger has given $800,000 of her own money for the initiative, but it's not clear if her plan is backed by any other deep-pocketed financial supporters. The California Parent Teacher Association, which supports the measure, could help generate grass-roots support throughout the state.
Munger was scheduled to address the statewide organization in Sacramento Monday afternoon.