WASHINGTON — The plan by House Republicans to vote today on repealing the new health care law is unlikely to succeed but sets the stage for removing or changing portions of the far-reaching legislation.

Meanwhile, Democrats on Tuesday set in motion a multipronged defense, including bringing people from the St. Louis area and around the country to testify how a repeal would harm their families.

Lori Bresnan of Ballwin told members of the Democratic Steering and Policy Committee that scrapping the law would bring hardship for her son, Sean, a college student who suffers from an immune system disorder. The new law lets him stay on the family's health plan until age 26.

Bresnan appeared alongside a mother with twin girls battling leukemia, a woman who lost health insurance while suffering from breast cancer and others who have benefited from the legislation signed into law last March.

"We are thrilled that we have the option to keep him on our insurance in this interim when families so often struggle to keep their kids covered or are left worrying about the health of an uninsured child," Bresnan said.

The repeal vote had been scheduled for Jan. 12. House GOP leaders postponed it for a week after the Arizona shooting attack that left six people dead and badly wounded Rep. Gabrielle Giffords, D-Ariz.

The repeal is expected to pass easily in the House, where Republicans hold a 242-193 advantage. But Democrats, who will control the Senate for another two years, have said they don't plan to take up the repeal.

The White House played down the vote, with spokesman Robert Gibbs saying it was not "a serious legislative effort."

The GOP legislation carries the hard-edged title "Repealing the Job-Killing Health Care Law Act." In the wake of the shooting, some Republicans appeared to tone down their rhetoric in the first of seven hours of debate. The website of Rep. John Boehner, R-Ohio, describes the law as "job-crushing" and "job-destroying."

House Minority Leader Nancy Pelosi, D-Calif., said she hoped that "in the wake of the real tragedy in Tucson, we come together with a renewed commitment to civility."

Republicans were nonetheless strong in their criticism, arguing that the law in coming years would intrude on Americans and saddle businesses with expensive regulation.

"This health care law, if left in place, will accelerate this country toward bankruptcy," said Rep. Paul Ryan, R-Wis., chairman of the House Budget Committee.

Echoed Rep. Todd Akin, R-Town and Country: "When you take a look at the federal budget and the level of spending on entitlements, it's a very frightening picture. The idea of the government taking over health care is a bridge too far for us."

While an outright repeal is not likely, the health care law should remain a center of debate for months, as GOP lawmakers move to do away with certain provisions. Democrats have left open the possibility of making changes in the law.

Sen. Claire McCaskill, D-Mo., said this month that she would be willing to consider proposals to compel people to have insurance other than the law's existing mandate.

A provision ripe for repeal requires businesses to file a 1099 tax form identifying anyone to whom they pay $600 or more in a year's time for goods or merchandise.

Rep. Jo Ann Emerson, R-Cape Girardeau, could play a role in ending the so-called "1099 mandate" in her new post chairing the House Financial Services subcommittee, which has jurisdiction over the Internal Revenue Service.

"Any kind of a small business — perhaps one run by a husband and wife — that uses multiple vendors would have to be responsible for that paperwork. All that paperwork, which might require an accountant, is going to cost money," she said.

Leading Democrats said Tuesday they were willing to make changes short of repeal. Those assertions were part of their defense of the new law, framing the proposed repeal as an attack on people's rights.

Rep. William Lacy Clay, D-St. Louis, took questions about the proposed repeal in a telephone town hall with constituents Tuesday night. He argued that the GOP plan would allow insurance companies to deny coverage for more than 250,000 people in his district with pre-existing conditions.

He contended that the repeal "would impose terrible human costs and the damage would be long-lasting."

The Health and Human Services department on Tuesday put out a report showing that as many as 129 million Americans under age 65 have pre-existing conditions. The release sought to underscore the risks of being rejected by insurance practices that the law seeks to curb.

Republicans experienced a rare break in their ranks when former Senate Majority Leader Bill Frist, R-Tenn., said this week that Republicans ought to drop the idea of repeal. Frist, a surgeon involved in a bipartisan effort to implement the law in states, said it has "many strong elements. And those elements … need to be preserved."