A deal limiting Iran's nuclear program in exchange for sanctions relief and international legitimacy will soon be in the hands of Congress, where lawmakers who want to block it face an uphill battle in spite of widespread skepticism over its provisions.

Most Republicans and some Democrats were not happy with how the deal was taking shape even before it was signed, believing that the Obama administration made too many concessions to Iran and wanted it too badly to drive a hard bargain. But the process for congressional review of an agreement is weighted in favor of approval, and Republicans will need strong Democratic support to keep it from taking effect -- something that's unlikely to happen.

Opponents are hoping they can change that dynamic by convincing voters that the agreement is a bad one which doesn't even meet its goal of keeping Iran from joining the exclusive club of nuclear-armed nations.

"If the American people register their discontent with a deal which is bad for world peace, I'm hoping that a lot of people vote against it," said Sen. Bill Cassidy, R-La.

President Obama's attempts to shut Congress out of the talks provoked a bipartisan backlash which resulted in enactment in May of a law giving Congress a say in any agreement. The law gives Congress 60 days to review the agreement and decide whether to accept or reject it. Lawmakers also can allow it to take effect without acting.

During that 60-day period, Obama can not exercise his authority under current law to waive existing U.S. sanctions enacted by Congress, though he retains full authority over any sanctions imposed by the executive branch. That limitation would become permanent only if Congress adopts a resolution of disapproval and is able to override an expected presidential veto.

The House Foreign Affairs Committee is poised to give the deal its first formal scrutiny, with a Tuesday morning hearing that Chairman Ed Royce said will begin the process of answering lawmakers' questions on the details.

"We'll be looking to see how the administration has done on Congress' red lines," the California Republican said. "Did we get anywhere, anytime inspections? Full Iranian transparency regarding its past nuclear activities? No large-scale, immediate sanctions relief; but guaranteed, workable sanctions snap-backs? Meaningful restraints on Iran's nuclear program that last decades?"

But lawmakers have been waiting until they have the deal in hand before deciding whether to pursue approval or disapproval, Senate Foreign Relations Committee Chairman Bob Corker told the Washington Examiner last week.

"We haven't really discussed how we go forward," the Tennessee Republican said. "There's been all kind of, I know, talk among lots of folks, but I can assure you there have been no formal talks with [ranking Democrat Sen. Ben Cardin of Maryland] or anyone else on the committee as to how we might deal with it."

One option that appears to have been discussed is to pursue an approval resolution, in the hope that its expected failure would show how little support the deal has on Capitol Hill. The advantage of that option is it would give Democrats a chance to express their disapproval of the terms of the deal without actually blocking Obama's signature foreign policy priority.

In a July 9 House Foreign Affairs hearing, Rep. Brad Sherman, D-Calif., hinted that lawmakers might proceed with that option, which also recognizes how little power Congress actually has to block implementation of a deal when the White House has lined up with the United Nations, other major world powers and even the Iranians to make sure it gets done.

"The administration appears to have lost sight of the true adversary in its ongoing battle with Congress," the Institute for Science and International Security wrote in a July 3 analysis that cited Iran's noncompliance with a November 2013 interim agreement and Obama administration efforts to explain it away.

As the agreement was taking shape, David Albright, founder of the nonpartisan group, which is widely cited for its technical expertise on nuclear issues, warned Corker's committee at a June 25 hearing that lawmakers should establish robust oversight and reporting requirements on the deal to ensure it meets its goal of preventing Iran from developing a nuclear weapon.

"This agreement warrants special and extreme congressional scrutiny," he said.