WASHINGTON (AP) — It started out a political "gotcha" — an amendment to President Barack Obama's health care law requiring members of Congress and staffers to get the same coverage offered to uninsured Americans. Wednesday, the administration tossed it back in the lap of Congress.

Proposed rules — issued when the halls of Congress are empty for summer recess — say lawmakers' offices should individually decide whether staffers are subject to a health law provision that would require them to switch their insurance from the federal plan to new coverage coming next year under Obama's overhaul.

The potential impact of the provision, authored by Iowa Republican Sen. Chuck Grassley, has been a huge source of anxiety for congressional staffers accustomed to getting their health insurance just like other feds, from the largest employer health care plan in the world.

The proposal does clarify that the government will continue to pay its standard share of premiums, resolving one of the biggest unknowns about the impact of Grassley's amendment. Many had been warning of a Capitol Hill "brain drain" if staffers were suddenly forced to foot the entire cost of their health insurance premiums.

But questions remain about such matters as retiree coverage and definitions of residency, so the prognosis for the fix is uncertain.

During the drawn-out debate over "Obamacare," Democrats kept insisting that their goal was merely to provide uninsured Americans with the same kinds of coverage and choices that members of Congress have. Grassley, in effect, dared his Democratic counterparts to swallow their rhetoric. A "no" vote on his provision would have undercut the argument that lawmakers supporting the law only wanted regular Americans to enjoy what they themselves had.

Under the amendment, lawmakers themselves and staffers in their personal, or "official," offices would have to exit the federal employee plan and get coverage through new health insurance marketplaces coming under the law. Also known as "exchanges," the marketplaces will offer subsidized private insurance to people who don't have access to a plan on the job.

But the amendment left many key details unclear — including whether the government would keep paying its share of premiums, which works out to around 75 percent.

The Office of Personnel Management, which runs the federal employee health plan, said lawmakers themselves are best equipped to decide which staffers are part of their "official" office. The term was not defined in Grassley's amendment, and the OPM said it turns out that congressional staffers in personal offices often also do part of their work for committees or as leadership aides. Those two categories — committee and leadership staffers — are exempt from Grassley's provision.

A senior congressional staffer familiar with the proposed regulations said several significant issues remain unclear or unresolved. One whole set of questions has to do with residency requirements. Some staffers, for example, may claim residency in their home state while living in Washington, D.C. What if health insurance plans in their home state don't have Washington-area providers in their networks? Other issues could impact coverage for retirees and those nearing retirement.

A spokesman for the federal personnel office refused an interview request, instead supplying prepared questions and answers that detailed aspects of the proposal.

The new insurance markets start will start signing up people on Oct. 1 for coverage that's effective Jan. 1. OPM said lawmakers will have to decide the status of their employees before the end of the year.

That could mean the difference between a routine re-enrollment or venturing into uncharted territory. Staffers waiting to find out might want to be extra nice to the boss in the meantime.