Add a new demand to the Democratic wish list for worker protections: Limits on erratic, unpredictable "just-in-time" scheduling.

Congressional Democrats would like to stop employers from hitting workers with short, odd, and unpredictable hours tailored to customer demand.

Leading liberals have called for legislation to crack down on the practices, prioritizing it with an increase in the minimum wage, paid family and sick leave and childcare as policies to highlight in the general election.

Democratic frontrunner Hillary Clinton bought into the idea in her economic speech earlier this month, saying that "fair pay and fair scheduling, paid family leave and earned sick days, childcare are essential to our competitiveness and our growth."

The idea to regulate workers' hours at the federal level is not new, but it is receiving added attention as Democrats push other labor market rules. The push also comes in the wake of high-profile news stories about workers struggling with schedules.

Last summer, Maria Fernandes, a 32-year-old woman who worked at three Dunkin' Donuts locations in New Jersey, was found dead in her car, where she had been sleeping, having inhaled fumes from an overturned gas can.

Although not directly tied to her death, the fact that Fernandes sometimes worked three shifts in a day, or both closed a shop and opened it up hours later the next morning, caused tough scrutiny for the chain's scheduling practices.

At the same time, the New York Times published a feature on workers with "on-call" or erratic schedules at Starbucks and other businesses.

Starbucks almost immediately responded by mandating that hours must be posted at least a week in advance, and tried to curb the practice of "clopening," meaning scheduling employees to close and then open the store the next day.

"A single mom should know if her hours are being canceled before she arranges for daycare and drives halfway across town to show up at work," Sen. Elizabeth Warren, D- Mass., said in introducing the Democratic legislation aimed at curbing such schedules.

The bill, the Schedules That Work Act, would prohibit companies from retaliating against workers who request schedule changes. It also would require employers in retail, cleaning and restaurants to provide schedules two weeks ahead of time and force them to pay extra if they make employees work on-call or split shifts.

The legislation faces no prospects of passing in the Republican-led Congress and is opposed by companies who warn that such mandates hurt business and lower employment. But, as with the minimum wage and paid leave measures, it is part of a suite of labor regulations that Democrats view as political winners.

"These policies are very popular. It's good policy and good politics," said Michael Wasser, senior policy analyst at the nonprofit group Jobs with Justice, which aligns with union goals.

Wasser said his organization has heard more from workers affected by unfavorable schedules as companies have turned to software that tracks periods of high customer demand and schedules workers accordingly. Jobs with Justice published a report in June finding that such practices were prevalent in D.C. for hourly workers, who got 32 hours weekly on average.

In a national survey, Susan Lambert of the University of Chicago found that nearly half of young part-time workers don't know what their hours are until within a week before work, and three-quarters face fluctuating schedules. The vast majority of working mothers and fathers with young children faced massively fluctuating hours, with their hours deviating from what would be normal by 40 percent on average. Lambert also concluded that unpredictable schedules can lower worker productivity and increase turnover.

María Enchautegui, a researcher at the Urban Institute who has studied the effects of unconventional work hours, went further, noting that erratic and unpredictable work schedules can prevent people from attending school or taking on second jobs. Her research has indicated that hours outside of the traditional nine-to-five hours correlate with more stress and less time with kids.

"We have to be very aware that this practice is not done by necessity by employers, it's a choice of employers," Enchautegui said.

She said, however, that she isn't aware of evidence that the problem is getting worse.

"I have yet to see a single shred of evidence suggesting this is getting worse over time," said Adam Ozimek, an economist at Moody's Analytics.

Ozimek said that greater priority should be placed on reducing unemployment and underemployment, which would give workers more bargaining power with which to improve their job conditions.

There's a "misconception that we can mandate good jobs by looking at every single qualitative aspect of a job and regulating what it can look like," Ozimek said. "If indeed you can manage to define jobs ... so narrowly and specifically that firms are really constricted and do have to offer a better overall package of wage and job quality, at that point you're going to be hurting employment overall."