A federal mandate for paid sick leave will be a major campaign topic in the 2016 elections, with a test vote in the Senate last week revealing support for the popular measure among vulnerable Republicans.

Fifteen Senate Republicans cast a nonbinding vote for an amendment to the GOP budget that expressed support for federal paid sick leave. In total, 61 senators voted for the measure offered by Sen. Patty Murray, D-Wash., more than the 60 required to overcome a filibuster.

In the vote, several swing-state Republicans endorsed at least the broad idea of a policy championed by President Obama in his State of the Union address and favored by Democrats, revealing an area in which Democrats have the side of popular opinion.

"We're not worked up over it, but it's disappointing that it got much that support, especially from Republicans," said Jack Mozloom, a representative for the National Federation of Independent Business.

There's no chance that Congress will pass sick leave legislation anytime soon, Mozloom said, but "we expect that it will be a campaign issue in '16."

The Republicans voting for the measure include Ron Johnson of Wisconsin and Pat Toomey of Pennsylvania, two generally conservative senators who face re-election in states that are at best purple, if not outright blue.

Mandating that companies pay their employees for days they are sick is a broadly popular policy. A January YouGov/Huffington Post survey found that 70 percent of U.S. adults favored the policy.

In January, ahead of his State of the Union address, Obama endorsed Democratic legislation that would require businesses with more than 15 employees to allow their employees to accrue one hour of sick time for every 30 hours worked.

That policy is favored by liberals and labor unions, who point out that the U.S. is among the few developed nations not to mandate some kind of paid sick leave.

More than one in three workers does not receive paid sick leave, according to the Bureau of Labor Statistics, including 22 percent of full-time employees. Only a quarter of part-time workers get paid sick leave.

The amendment adopted by the Senate last week does not specify the terms of the paid sick leave.

Johnson's office did not respond to a request for comment Wednesday. Toomey has backed a bill, introduced by Sen. Mike Lee, R-Utah, that would allow employees to trade overtime hours for paid time off, something that is not permitted under current law.

Allowing employees to accrue paid sick leave based on the amount of overtime worked has the support of the National Federation of Independent Business, Mozloom said.

But the organization opposes a paid sick leave mandate based on normal hours worked, on the grounds that small businesses couldn't "absorb" the costs. Many small businesses employ few enough workers that paying for one to be out for an extended period of time would require the business to hire a temp or reduce its output.