On the eve of the 11 th anniversary of the Sept. 11, 2001 terrorist attacks, and as the federal government formally recognized the link between harmful toxins at Ground Zero of the World Trade Center and the risk of cancer for first responders, one legislator's opposition to a bill to provide medical care for people exposed that day is adding to the narrative of the 2012 election.

Rep. Paul Ryan, the Republican nominee for vice president, voted July 29, 2010 against the James Zadroga 9/11 Health and Compensation Act when the measure first came up for a vote in the House of Representatives. In order to expedite consideration of the bill, the House Democratic leadership considered the measure under suspension of the rules, requiring a two-thirds majority for passage. Support for the bill fell short, 255-159.

Eight weeks later on Sept. 29, when the $7.4 billion package returned to the House floor under regular order, Ryan voted no again. This time, however, the bill was considered under a rule, requiring only a simple majority for passage, and was sent on to the Senate.

The Democrat-controlled Senate made its changes to the bill and the House voted on final passage during the lame duck session on Dec. 22, 2010. Ryan, along with 167 other members of the House, did not vote on final passage in the House, having already skipped town to return to their congressional districts for the holidays.

Ryan explained in a floor statement that he would have opposed the final passage vote, too, calling the bill "deeply flawed." He also complained that it "would create a new health care entitlement, the World Trade Center Health Program, while also extending eligibility for compensation under the September 11th Victim Compensation Fund of 2001."

Now, almost two years later, congressional Democrats are citing Ryan's opposition to the bill as "another example of Ryan's extreme ideology."

"This bipartisan law is crucial to the families and victims of 9/11 and will be a painful thorn in the Romney campaign's side as our nation comes together again on the 11th anniversary of the attacks," one senior Democratic aide told ABC News.

The fire and collapse of the World Trade Center's twin towers contaminated the nearby air with particles of glass, asbestos, cement, lead, gypsum, calcium carbonate, other metal particles and other toxins. The National Institute for Occupational Safety and Health, which determines which cancers are covered under a fund established to care for first responders to the attacks, initially included just a short list of illnesses - but not cancer - that qualified for compensation. Still, the bill allowed for other health conditions to be added over time and today's announcement adds two-dozen types of cancer to a range of illnesses covered by the law.

President Obama signed the legislation into law Jan. 2, 2011.