Republicans may have promised to repeal or at least do a big makeover of Obamacare now that they control both the House and the Senate, but most experts believe it’s lip service only.

The 2010 Affordable Care Act is in full force across the country, with internet-based health insurance exchanges up and running, expanded Medicaid in 28 states and strict new requirements for health insurers. Here are five reasons the GOP-led Congress won’t be able to change much.

The veto.

This is the big one: President Barack Obama still has veto power. Republicans may have a majority in the Senate, but they don’t have the 60 seats needed to override a Democratic-led filibuster or a presidential veto. And Obama’s not going to allow his signature piece of legislation to be gutted.

They like it.

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Republicans actually like a lot about Obamacare. It’s great business for health insurance companies, which in turn give plenty of money to Republicans. Republicans have also always agreed that more Americans need to be covered by health insurance. They just haven’t always agreed on how to get there.

“The five major national health insurers have all seen their stock price at least double — one has almost tripled — since the ACA was enacted, and they’ve all been raising their earnings estimates,” says Jay Angoff, who helped construct health reform at the Health and Human Services department before returning to private law firm Mehri & Skalet. "Republicans are not going to try to repeal a law that has been such a boon to insurers: They are still a Republican constituency group."

Voters like it.

Ask voters if they like Obamacare, and many will say no — 48 percent in the latest NBC News poll. But ask about specific provisions, and they’re very popular. People like laws that prevent insurance companies from pulling their insurance just as they become really sick and need it. They like provisions that allow young adults to stay on their parents’ plans. And they really like government subsidies.

It’s too late.

As many as 10 million people already have health insurance on the exchanges The Congressional Budget Office projects that 26 million people will buy health insurance on the exchanges by 2022 and that 12 million people will become newly eligible for Medicaid in the states that choose to expand their offerings by 2022. It would be difficult to take insurance away from that many people.

They can just tweak it.

There are several provisions that Republicans can get support from Democrats on, including perhaps introducing some really cheap plans called “copper” plans, that won’t cost much and also won’t cover much; loosening the requirements that most employers provide health insurance and perhaps changing the definition of part-time worker from the current 30 hours a week; and perhaps allowing people to renew bare-bones plans that don’t comply with the healthcare law’s requirements.

None of these items will stop the House of Representatives from voting to repeal Obamacare, and it may be one of the first actions taken in January. “At some point next year we’ll move to replace Obamacare,” House Speaker John Boehner promised Thursday. But the House has already voted more than 50 times to repeal the law, with zero effect.

And, of course, the Supreme Court just might do the job for the GOP, with its decision to consider a suit filed against the federal subsidies. If the court rules next year that the subsidies are unconstitutional, the administration will have to scramble to find another way to help people pay for health insurance.