Stockton, a suburban outpost of about 310,000 people in California, may seem at a first glance like an unlikely place for a social experiment at the cutting edge of political thought.

A moderate Central Valley city sandwiched between the overwhelmingly liberal Bay Area to the west and more conservative and agricultural counties to the east, it has never been seen as a political bellwether for a state increasingly known for its progressive politics.

But Stockton has faced levels of economic hardship that separate it from many of the thriving municipalities just an hour or two away: it was the largest in the country to declare bankruptcy in the years after the recession, and it still suffers from high rates of poverty, foreclosures and violent crime. It is statistics like these that make it well situated for a test run of an idea percolating in idealistic circles in recent years as a way to reduce economic hardship: a universal basic income, a program to guarantee no-strings-attached money to certain swaths of the population.

The idea has grown in popularity, both on the left and among some more conservative-leaning corners of Silicon Valley.

Mayor Michael Tubbs — at 27, the city's first black mayor and one of the youngest of any race for any comparably sized city in the country — will soon unroll an experiment to give $500 cash every month to a select group of families for about 18 months. The project, which will begin in 2019, is being funded by $1 million from the Economic Security Project, a philanthropic group helmed in part by Facebook co-founder Chris Hughes.

Tubbs has spoken about his familiarity with the issue of basic economic need. His mother was on welfare for the first five or six years of his life, he has said, and he said he believes the program could help people like her.

"I think something like this could help the majority of Americans," Tubbs said. "And that's why I'm proud to introduce this in Stockton, where plenty of people are working hard like my mother, but might not have money lined up for a rainy day or rising rents or anything like that."

But he has acknowledged that the idea is an experiment with unknown outcomes.

Similar income experiments have taken root in other places, including trials of varying scope and implementation in Finland; Oakland, Calif.; and Ontario.

But with the relatively disparate studies and small sample sizes, a strong consensus has not yet emerged about its success or failures.