It started in New York City as what seemed a quixotic drive confined to fast-food workers. But the movement to raise the hourly minimum wage took root in other parts of the country, and is emerging as a significant, and divisive, element in the presidential campaign.

Just this week, workers in Los Angeles County and Washington, D.C.; employees of fast-food chains in New York State; and members of the University of California staff all learned that they may soon be earning at least $15 an hour, more than double the federal minimum wage of $7.25. Several other cities — including Chicago, Kansas City, Mo., Los Angeles, San Francisco and Seattle — have already raised the lowest legal wages paid to workers in those places.

Now, the minimum wage has carved out a major presence in the presidential election. Republicans and many business owners are dead set against it, but the issue has taken a central spot in the stump speeches and public pronouncements of Democratic candidates, for whom giving the middle class a “fair shot” has become a mantra.

One of those candidates, Senator Bernie Sanders, independent of Vermont, introduced a bill on Wednesday that would raise the federal minimum wage to $15 an hour. Mr. Sanders, more than any other contender for the Democratic nomination, has highlighted the subject repeatedly during his campaign, and he did so again at a rally in Washington on Wednesday where he discussed the bill.