The burning question that no one asked Hillary Clinton in the debate

The Democratic candidates for president hashed out their differences on gun control, the Iraq war and more in CNN's primary debate Wednesday night. Yet the minimum wage, one of the most important divisions between the contenders, came up only in passing.

The foremost candidates -- Sen. Bernie Sanders (I-Vt.), former Maryland governor Martin O'Malley, and former secretary of state Hillary Rodham Clinton -- all believe the national minimum wage of $7.25 an hour should be raised. The issue is by how much.

Sanders and O'Malley have thrown their support behind a national movement to set the floor at $15 an hour. This movement has galvanized workers both in and out of unions in cities across the country, and has already claimed victory in the Pacific cities of Los Angeles, San Francisco and Seattle.

While Clinton agrees the national minimum wage should be higher than it is now, she hasn't said to what specific level she thinks it should be raised. Earlier this year, she called into a conference of labor organizers who had gathered in Detroit to advocate for the $15 hourly minimum, but she didn't specifically endorse their goal, and she hasn't since then, either. She's spoken approvingly of legislation in Congress that would increase the minimum wage to $12 an hour nationwide, but whether she would support a minimum wage above that figure is an open question -- a question no one asked her during the debate.

Clinton might have good reasons for her reticence. While a large body of economic evidence suggests that raising the minimum wage really does benefit workers, those studies have focused on relatively small changes. Raising the national minimum wage to $15 would more than double the amount that employers must pay their workers in many areas.

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