People have begun casting ballots in Phoenix's mayoral race and on four ballot measures, including a proposed $31 billion transportation plan that includes expanding the city's light rail line.

Voting in Phoenix municipal races began Saturday, continues on Monday and wraps up at 7 p.m. Tuesday.

Incumbent Democrat Greg Stanton is seeking a second term as the city's mayor in a race against Republican Anna Brennan and independent Matt Jette.

City Council member Daniel Valenzuela is facing a challenge from Felix Garcia in the race for the city's District 5 seat.

The transportation plan, known as Proposition 104, would increase a transit sales tax that would be used to expand the city's light rail line and bus service, repair and build roadways, and create bike lanes.

Proponents said the 35-year plan would provide people in Phoenix with more choices on public transportation and help the city keep up with its growing needs.

Opponents said it's not prudent to put money into a light rail system that isn't widely used and said the plan would hurt businesses located near light rail construction projects.

The plan would be funded by the proposed transit sales tax increase, passenger fares and federal and county funds.

The transit sales tax is now 0.40 percent.

It would be raised to 0.70 if the measure is approved, translating to 70 cents on a $100 purchase.