The issue of federal employees' pay could soon hit the presidential campaign.

Mitt Romney's spending plan includes a pledge to "align federal employee compensation with the private sector," and it cites studies showing that "federal compensation exceeds private sector levels by as much as 30 to 40 percent when benefits are taken into account. This must be corrected."

As far as President Obama's campaign is concerned, that means Romney is talking about a federal pay cut of up to 40%.

"To pay for tax cuts for millionaires and billionaires, (Romney) drastically cuts pay for the men and women who secure our borders and skies, enforce our laws, inspect our food and search for better treatments and cures," said Obama spokesman Adam Fetcher.

Obama's debt reduction plan, he said, "requires federal workers to do their part through eliminating wasteful spending, streamlining government and freezing federal pay for the past two years."

Romney aides and supporters said they are not proposing a 30% to 40% pay cut, and federal compensation involved more than take-home pay, including such benefits as health coverage, retirement, paid leave and student loan repayments. According to the Romney plan, aligning federal compensation with the private sector will save $47 billion.

Romney spokesperson Amanda Henneberg said $5 trillion has been added to the national debt during the Obama administration, and Romney has a plan to address the "runaway spending" slowing the economy.

"Part of that plan is to ensure that compensation for federal employees is comparable to similar workers employed outside of government," she said.

In recent years, disputes over federal pay and benefits triggered major political battles in Wisconsin and Ohio.

The same could soon happen in Washington.