SACRAMENTO — Gov. Jerry Brown is maintaining a substantial edge over Republican challenger Neel Kashkari as he makes is bid for an unprecedented fourth term, according to a poll released Tuesday.

The Public Policy Institute of California survey found the Democratic governor with a 21 point lead among likely voters, up 2 percentage points from a similar poll taken after the June primary.

Brown led Kashkari 54 percent to 33 percent, according to the survey of 916 likely voters, which was conducted by telephone from Sept. 8-15. The part of the poll focused on likely voters has a sampling error margin of plus or minus 4.9 percentage points.

Brown also has more support from women voters, 59 percent, and Latinos, 74 percent.

Meanwhile, likely voters say they support Proposition 1, the $7.5 billion water measure, by a 2-to-1 margin.

The institute’s survey found that 58 percent of voters planned to vote for it, while 29 percent would vote against borrowing to pay for water projects. Proposition 1 was placed on the ballot by overwhelming bipartisan votes in the state Assembly and Senate.

Proposition 47, which would reduce penalties for some drug and property offenses from felonies to misdemeanors, had the supported of 62 percent of likely voters.

Support for two other ballot measures was more tepid.

Another measure placed on the ballot by the Legislature, Proposition 2, would create a rainy day fund with a reserve dedicated to education. It was favored by 43 percent of voters, while 33 percent said they would vote no and nearly a quarter were undecided.

Proposition 45 would allow the state insurance commissioner to review rate changes. The poll found 48 percent of those surveyed would vote yes, 38 percent no, and 14 percent were undecided.

The poll also found voters to be in a better mood than they were before the last statewide election two years ago, with 43 percent of likely voters believing the state is generally headed in the right direction, up from 29 percent two years ago.

Approval of the Legislature also is up, despite a year marred by two federal corruption cases, a perjury conviction and a drunken driving arrest near the state Capitol. Each of those cases involved Democrats in the state Senate. Still, 32 percent of likely voters approve of the Legislature’s job performance, up from 22 percent two years ago.