Already, the political dynamic on health care has started to change. Though Democrats still face a skeptical public, Republicans have a greater burden.

The GOP still may be able to score points against vulnerable Democrats by decrying the admittedly high cost of President Barack Obama’s landmark bill and noting it will be financed with increased taxes. But Republican threats to repeal it if they retake Congress in November also put them in the politically difficult position of threatening to take away millions of Americans’ newly won rights.

The bill Obama signed Tuesday will quickly allow insurance coverage for those with pre-existing medical conditions, let young adults stay on parents’ insurance until age 26 and give seniors additional help in paying prescription drug costs now limited by Medicare’s so-called “doughnut hole.”

As someone with a 23-year-old son and a substantial Medicare drug bill, I can attest these are not small things.

Even before the final vote, Democrats were previewing their post-passage tactics by distributing a list of benefits with high public support and asking which ones Republicans wanted to repeal. Beyond that, threats of repeal by top Republicans will accentuate the party’s reputation for negativism when there is no realistic way they could succeed any time soon.

Even with congressional control, any such effort next year would encounter Obama’s opposition. Ultimately, any successful repeal effort would require electing in 2012 a president willing to take the political gamble of advocating the end of expanded coverage for millions of Americans.

To be sure, the long reform campaign still has one more legislative barrier — and potential legal ones. That’s Senate consideration of the so-called “reconciliation bill” that improves the initial measure by removing some of the crasser deals that got it through the Senate just before Christmas.

Any Republican successes won’t change the fact that the landmark bill extending health insurance to more than 30 million additional Americans has become law and that a Democratic Congress and president have fulfilled their party’s long-standing promise.

So what problems remain beyond the final legislative maneuvers and any continuing efforts by critics to misrepresent provisions in the measure?

A crucial factor will be implementation, something Obama stressed in hailing House passage Sunday night. The measure’s complexity, illustrated by the confusing, yearlong debate, means the administration must mount an intensive education campaign to show Americans how to benefit.

In addition, this and future administrations face the continuing challenge of resolving the long-term fiscal problems of Medicare, Medicaid and Social Security, even if this bill achieves its promised budgetary savings. Increased taxes and decreased benefits for future retirees are almost inevitable.

Perhaps the biggest short-term threat is the vow from some critics to switch the battlefield from Congress to the federal courts. On Tuesday, 13 Republican attorneys general, including Texas’ Greg Abbott, and one Democrat filed a federal court suit challenging the bill’s constitutionality because of the requirement that every American buy health insurance or pay a penalty.

Given the fact that the federal courts in general, and the Supreme Court in particular, are dominated by Republican presidents’ nominees, the judiciary could play havoc with the health insurance plan. But the White House seems confident that won’t happen, and it’s ironic that those who decry judicial activism would have the courts curb or reject a law that resulted from the actions of the voters and their elected representatives.

In the end, some House Democrats who supported the bill will lose their seats in November. Of course, that was always likely, with or without health care, primarily because their districts are too Republican.

And the Democrats now have a chance to turn the tables politically on the GOP because it will be far easier to show people what this legislation will do for them than to decry its passage.

— Carl P. Leubsdorf is the former Washington bureau chief of the Dallas Morning News. carl.p.leubsdorf@gmail.com