WASHINGTON — In an election year dominated by socioeconomic themes, it seems logical that raising the federal minimum wage would become a heated campaign issue in the battle for the presidency. Stagnating wages and the increasing concentration of wealth among the nation's highest earners have prompted calls to boost the purchasing power of American workers. At $7.25 an hour, a full-time federal minimum-wage earner makes about $15,080 a year, which is below the federal poverty level for a two-person family.

WASHINGTON — In an election year dominated by socioeconomic themes, it seems logical that raising the federal minimum wage would become a heated campaign issue in the battle for the presidency. Stagnating wages and the increasing concentration of wealth among the nation's highest earners have prompted calls to boost the purchasing power of American workers. At $7.25 an hour, a full-time federal minimum-wage earner makes about $15,080 a year, which is below the federal poverty level for a two-person family.

But neither President Barack Obama nor Republican presidential candidate Mitt Romney has said much about the minimum wage, though Obama once called for raising it to $9.50 an hour by the end of 2011 and Romney supported indexing it for inflation earlier this year until conservatives cried foul.

In the absence of a prominent push to boost the federal minimum wage, states and local governments have picked up the slack: Eighteen states and the District of Columbia now have minimum wage rates that are higher than the federal level.

Oregon's minimum wage increased to $8.80 an hour on Jan. 1. Santa Fe, N.M., and San Francisco boast the nation's highest minimum wage rates, at $10.29 and $10.24 per hour, respectively.

Though it typically enjoys strong public support, raising the minimum wage is always contentious.

Some economists say increases spur more consumer spending, which helps the economy and ultimately creates jobs. Others say the rate increases hurt job creation during economic downturns and put a drag on hiring when the economy is strong.

As the three-year anniversary of the last federal minimum-wage hike arrives today, a coalition of labor, religious and women's groups is preparing to fight for an increase once again. The activist groups are launching a nationwide campaign to raise the federal minimum wage, starting with a national "Day of Action" today.

Marches and rallies are planned for today at congressional district offices and at businesses that pay low wages. Events are planned in dozens of cities, including Chicago, New York, Washington, D.C., Miami, Kansas City, Mo., Sacramento, Calif., and Philadelphia.

Democrats in Congress also are weighing in. Rep. George Miller, D-Calif., soon will introduce legislation to raise the federal minimum wage by 85 cents an hour for three straight years — taking it from $7.25 to $9.80 per hour — and then index it annually for inflation thereafter. Sen. Tom Harkin, D-Iowa, and Rep. Jesse Jackson Jr., D-Ill., already have introduced similar bills. The proposals would provide raises for about 28 million people, according to estimates by the nonprofit Economic Policy Institute.

The Republican-led House of Representatives isn't likely to pass such a proposal, but the Democratic-controlled Senate might. Democrats surely welcome the chance to portray the GOP as insensitive to the needs of working Americans.

"It's a classic election-year ploy to make the Democrats look like they're protecting low-income workers. I think it's well understood that raising the minimum wage hurts workers on the lower end of the pay scale in that it does kill jobs," said a recent statement from Randy Johnson, the senior vice president for labor, immigration and employee benefits at the U.S. Chamber of Commerce.

In today's dollars, the inflation-adjusted value of the minimum wage in 1979 was $8.51 an hour, according to researchers at the Center for Economic and Policy Research.