Don't let the nastiness in Congress over the past few days obscure an important fact: Millions of Americans can now begin signing up for affordable health insurance.

Online marketplaces open in all 50 states Tuesday. With the help of federal subsidies, the nation will have near universal coverage. The Affordable Care Act has a very good chance of being successful, and the nation will be better off because of it. When people have insurance, they tend to get care sooner and have regular physicians instead of relying on emergency room care. That saves money in the long run.

There will be problems with implementation, and some of those problems may be severe. The government is putting an enormously complicated project in place on a tight deadline in the face of fierce and often illogical opposition from the tea party wing of the Republican Party. Even though states could design their own exchanges, the federal government is doing so in 36 states, including Wisconsin, mostly because of Republican opposition.

We continue to have concerns that the law is less focused on cost control _ the major long-term problem the nation faces _ than it is on extending coverage. But that said, the opening of online health insurance markets is a major accomplishment and should allow most of the uninsured to find affordable private insurance coverage with the help of government subsidies. Enrollment begins Tuesday for coverage that would begin Jan. 1.

Insurers are offering four tiers of coverage: bronze, silver, gold and platinum. The plans differ in how much the premiums cost and the amount of the bill that insurers pay. A bronze plan, for example, will cover 60 percent of eligible medical expenses; a platinum plan will cover 90 percent.

In Wisconsin, a family of four with an income of $50,000 would pay $282 a month for the second-lowest cost "silver plan" after the tax credit. It would pay $106 for the lowest "bronze" plan after the tax credit. Those rates are roughly in line with what the market is now charging, although insurance experts caution that the actual rates people pay will depend on such factors as age, income, insurance company and place of residence. Tax credits are taken off the price at the time of purchase and are available whether the buyer owes federal taxes or not.

Republicans continue to resist Obamacare _ some cartoonishly (see "Ted Cruz" and "filibuster"). A wide philosophical divide remains in Congress and will not be closed anytime soon. But it's worth recalling two facts:

The U.S. Supreme Court upheld Obamacare, and the president won re-election after his opponent made repealing the law a major plank in his platform.

Threats to shut down the government or _ worse _ to fail to extend the debt ceiling and flirt with default over this law are sheer folly and reveal an opposition more concerned with its own interests than the broaders interests of the American people.

Obamacare is here to stay. Improve it. Make it work.