The Affordable Care Act was designed with two major objectives: It was supposed to extend health insurance to people who had been uninsured, and it was supposed to create a competitive marketplace that would lower costs over time.

Maine has fallen short on the first goal, but don’t blame Obamacare. Gov. LePage and Republican allies in the Legislature have blocked Medicaid expansion, refusing the federal funds that would have been used to cover 60,000 people. As a result, Maine was the only state in the country that failed to lower the rate of people without health insurance between 2010 and 2014.

That’s an embarrassment, but we can be more hopeful about progress on the second objective.

Aetna announced that it wants to sell individual plans on the Maine insurance exchange. In nine counties (including Cumberland, York and Sagadahoc), Aetna would join Anthem Blue Cross and Blue Shield, Harvard Pilgrim and Community Health Options to serve residents who buy their insurance in the Obamacare marketplace.

Four companies competing for business will have a strong incentive to keep rate increases to a minimum by controlling costs. Under the market reforms of Obamacare, companies can’t do that the old way, which was to deny service to people with pre-existing conditions, or dump patients when they got too sick.

The companies that win in this competition will be the ones that offer the lowest rates because they have policies that promote the long-term health of their plan members, and the best customer service that keeps their healthy customers loyal. As long as there is that kind of competition in the marketplace, there will be pressure on insurance companies to keep people healthier and happier.

Maine has a long way to go to reduce the number of people without insurance. Especially troubling is the percentage of children who are uninsured, which increased from 4 percent in 2010 to 6.3 percent in 2014 as a result of Gov. LePage’s cuts to social services.

But it’s encouraging to see private-sector businesses competing to serve the expanded pool of people who can now afford insurance because of the Affordable Care Act. It’s good to see progress toward at least one of Obamacare’s main objectives.