WASHINGTON - The Senate overwhelmingly gave the final sign-off Tuesday on legislation designed to aid veterans fighting diseases they believe are linked to toxic exposure, particularly those who served in the Iraq and Afghanistan wars.

On a 86-11 roll call, the vote served as a political surrender by Senate Republicans, a week after they blocked consideration of the popular legislation seemingly out of political pique because Democrats clinched a party-line deal on an unrelated massive domestic policy bill that could be considered later this week.

Republicans tried for several days to contend last Wednesday's blockage of the PACT Act, as it is officially known, had to do with a technical argument about which portion of the federal budget would fund $280 billion worth of new allocation for veteran health programs.

But 25 Republicans who had recently supported the exact same bill switched their votes last Wednesday, less than an hour after Senate Majority Leader Chuck Schumer, D-N.Y., and Sen. Joe Manchin, D-W.Va., announced their deal on the ambitious legislation unrelated to the PACT Act.

Republicans absorbed a series of political blows, led by comedian and activist Jon Stewart and several prominent veterans groups, that, by lunchtime Tuesday, left many ready to settle the matter and vote to send the legislation quickly to President Joe Biden's desk.

"He just beat the daylights out of them," Schumer said Wednesday in a celebratory visit to a couple of dozen veterans who have set up a vigil on the Capitol's north lawn since last week's failed vote.

Democratic leaders allowed Stewart and dozens of veterans, their families and other supporters into the chamber's public gallery for the final series of votes - something that has happened less than a handful of times since the onset of the global pandemic in March 2020 prompted officials to not allow the general public into the House and Senate galleries.

In the end, 37 Republicans joined 49 members of the Democratic caucus to vote for the legislation, which compels the Department of Veterans Affairs to presume that certain illnesses came from exposure to hazardous waste incineration, mostly focused on the issue of burn pits from recent wars in Iraq and Afghanistan.

That would remove the burden of proof from the injured veterans.

Sen. Patrick Leahy, D-Vt., missed the vote because of a recent hip-replacement surgery.

In the final moments of debate, the activists grew emotional. Stewart, who took up the cause following a similar effort he helped lead for first responders who suffer lingering effects from the 9/11 site, put his head in his right hand and started to cry as the roll call began. The crowd lit up with brief cheers when the gavel fell, getting quickly admonished by officials for breaking decorum that requires silence.

Asked to explain the GOP reversal, Minority Leader Mitch McConnell, R-Ky., offered no broad explanation and acknowledged the legislation would pass with broad support.

"Theses things happen all the time with the legislative process," McConnell told reporters at his weekly news conference, conceding defeat. "I think in the end the veterans service organizations are going to be pleased with the final result."

Sen. Jon Tester, D-Mont., chairman of the Senate Veterans Affairs Committee, credited the veterans groups and Stewart with taking what was previously a relatively obscure health issue and turning it into a national cause.

"That's who really did it, that's who elevated it," Tester said as he joined Schumer at the impromptu celebration outside the Capitol.

Biden also gave the issue prominence in his March State of the Union address, followed by a trip to a Texas community the following week to drive home its importance.

"We're following the science in every case, but we're also not going to force veterans to suffer in limbo for decades," Biden said during the March visit to Texas.

In his remarks, the president has noted that his son, Beau, served in the Army in and around Baghdad as a judge advocate general in the Delaware Army National Guard, on bases where waste was burned in an open-air site.

The state's attorney general, Beau Biden died in 2015 from brain cancer, although no diagnosis ever connected the cancer to his service in Iraq or other overseas postings.

In a sign of his own devotion to the issue, the president planned to surprise the veterans holding vigil outside the Capitol over the weekend with a pizza delivery, but he tested positive for a rebound coronavirus case and resumed his quarantine.

Instead, Veterans Affairs Secretary Denis McDonough arrived with the pizza to the group.

Experts are often uncertain of the direct link between specific cancers or diseases and the burn pits in Afghanistan and Iraq, where the military often burned large amounts of waste - including plastics, batteries or vehicle parts - that released plumes of dangerous chemicals into the air.

Veterans then have to prove there is a direct connection between their cancer and the burn-pit chemicals, a threshold that can at times be difficult to meet, particularly if the condition doesn't develop until years after a deployment. Studies have shown that Veterans Affairs rejects the vast majority of claims.

"You could talk to any one of these people and they would say we would rather not be here."

Schumer took a similar approach, happy the legislation finally passed.

"All's well that ends well."