Instead, advocacy groups see the legislation as the beginning of a broader campaign that may span years. In at least eight states so far this year, a proposed increase in the state pay floor has cleared either the Senate or House, according to the National Conference of State Legislatures.

The federal minimum wage hasn't been increased since 2009.

Vote postponed

Senate Majority Leader Harry Reid postponed a vote in his chamber earlier this month to give labor unions more time to organize support, said a leadership aide who sought anonymity to discuss strategy.

A Senate vote — especially with no House action expected amid Republican opposition — would create a list of targets for interest groups. This makes a decision on the vote a complicated choice for Reid, and for Democratic senators seeking re-election in states that voted Republican in the 2012 presidential contest.

If those senators vote no, they could suppress Democratic turnout. If they vote yes, they give opponents an issue to use against them.

"Right now each side is trying to shape the landscape around targeted lawmakers in states and districts," said Republican strategist Ron Bonjean, who was an aide to former Senate Majority Leader Trent Lott. "There's much more activity on the grassroots and communications level." Lott is now a lobbyist at Patton Boggs.

Four Democrats

At least four Democrats seeking re-election next year have expressed reservations about supporting a $10.10 minimum wage. They are Mark Pryor of Arkansas, Mary Landrieu of Louisiana, Mark Udall of Colorado and Mark Warner of Virginia. Landrieu and Pryor are running in states Obama lost in 2012.

Senator Joe Donnelly, an Indiana Democrat, said he too hasn't made up his mind about the proposal Democrats have put on the table.

"We're looking at it pretty carefully," Donnelly said in an interview in which he said he supported the concept of an increase. "We're going to wait to see the legislation."

The perception that a federal wage increase is more of a political talking point than a real possibility saps enthusiasm from some senators who might be willing to work on the issue.

Senator Lisa Murkowski, an Alaska Republican who occasionally crosses party lines on issues, said Reid has said he will bring the federal minimum wage bill straight to the Senate floor without a committee vote. That is a deviation from the typical process, she said.

'Not legislating'

"To me that's not legislating," Murkowski said in an interview. "That's an effort to message on an issue that the majority feels is going to be beneficial to them in an election. That's not why I'm here. So whatever."

Murkowski said she hears far more about a ballot measure in Alaska that would tie the state's $7.75-an-hour minimum wage to inflation after 2016.

"There's a lot of folks that don't have any appreciation at all that we're doing this on the federal level," Murkowski said. "They know that we have got an initiative on the primary ballot and are paying attention to that."

In addition to Alaska, state minimum wage increases are on the ballot or are being considered in South Dakota, Arkansas, California, Idaho, Massachusetts and Missouri, according to the Ballot Initiative Strategy Center, a Washington-based group that tracks voter initiatives.

State wages

Twenty-one states and the District of Columbia have set their minimum wages above $7.25 an hour. The highest state level is currently $9.32 in Washington state, which in 1998 enacted an increase linked to the cost of living over opposition from retailers, restaurants and hotels.

Democrats see an advantage on the issue. Sixty-nine percent of Americans, including 45 percent of Republicans, support the president's call to raise the federal minimum wage to $10.10 over the next three years, according to a Bloomberg National Poll released March 12. Twenty-eight percent of poll respondents oppose such action.

Six U.S. Senate candidates endorsed by Emily's List are campaigning on the issue, said Marcy Stech, a spokeswoman for the Washington, D.C.-based group that supports Democratic women candidates who back abortion rights. So are an "overwhelming majority" of the 22 House contenders and six gubernatorial candidates endorsed by the group, she said.

895 commercials

The minimum wage is the subject of campaign television commercials airing in Texas, Arizona, Illinois and New Jersey. So far, 895 commercials on the topic have run in those states, according to data complied by New York-based Kantar Media's CMAG, which tracks advertising.

The desire to talk about the issue in the states rather than in Washington is sending some federal officials out of the nation's capital.

Labor Secretary Thomas E. Perez went to Cambridge, Massachusetts last week to promote small businesses that support a boost to the minimum wage. Several weeks earlier, Massachusetts Senator Elizabeth Warren had held a similar event in Boston with second-ranking Senate Democrat Dick Durbin of Illinois.

Another reason for the slow lobbying in Washington has to do with congressional appetite — it's difficult to focus on two similar issues at the same time. Just last week Senate negotiators agreed on a plan to extend unemployment benefits for the long-term jobless, a priority for many of the same groups pushing for a minimum-wage increase.

"This unemployment insurance fight has gone on much longer than any one thought it would," said Judy Conti, federal advocacy coordinator at the National Employment Law Project, a Washington-based group coordinating efforts to raise hourly pay.

Any good lobbying effort focuses on members who may be willing to support an issue. That may be why Republican Senator Ted Cruz of Texas hasn't heard much on the minimum wage.

"If they are out there, they aren't talking to me about it," he said.

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