PORTLAND — A Republican congressman is brushing off criticism from conservatives angry that he didn’t vote to repeal President Barack Obama’s health care law.

U.S. Rep. Bruce Poliquin of Maine joined Reps. Bob Dold of Illinois and John Katko of New York to become the only three Republicans to vote this week against a proposal to repeal the Affordable Care Act.

Poliquin said he opposes the law but believes a replacement plan needs to be developed first. Furthermore, the House has voted several times to repeal the law and it has never become a reality, he said.

“Insanity is doing the same thing over and over again and expecting a different result,” the freshman representing the vast, rural 2nd District said Friday. “I’m doing exactly what I told the voters I would do, which is to come down here and fix problems.”

Some conservative groups are condemning Poliquin for his action, including the national board of the libertarian-leaning Republican Liberty Caucus, which voted Thursday to rescind its endorsement of him.

“We were both stunned and disappointed by Rep. Poliquin’s vote,” Matt Nye, national chair of the Republican Liberty Caucus, said in a statement. The Campaign for Liberty, a group founded by former Texas Rep. Ron Paul, also slammed Poliquin this week, saying he broke his pledge to “support and cast every vote for legislation that will repeal or defund ObamaCare.”

The House voted 239-186 to repeal the health care law.

All three of the Republicans who voted against the measure were elected in districts won by Obama.

Katko also said he would vote to repeal Obama’s health care law if there’s a replacement.

Dold previously opposed the Affordable Care Act but said it’s time to stop talking about its flaws and to start talking about fixing them. “Casting yet another symbolic vote for full repeal of the law, without any replacement legislation, simply distracts us from the work that must be done to drive costs down, restore access to care and make healthcare work for everyone,” he said in a statement.

Poliquin said during his 2012 Senate campaign that one of his priorities in Congress would be to repeal the health care law, but has stressed more recently the need to fix the existing law.

The congressman wants to replace the law with a “free-market alternative,” like one outlined by some GOP members this week that would eliminate insurance marketplaces and abolish taxes the law imposes on medical devices, among other things.

Poliquin hasn’t endorsed the plan, but said any replacement must require health insurance companies to cover people with pre-existing conditions and help the more than 60,000 Maine residents who already have signed up for coverage on the exchange.

Nye dismissed the idea that Congress must pass an alternative plan before the health care law can be repealed.

“Poliquin’s reasoning is analogous to cutting off your arm at work and saying you’re not going to stanch the bleeding until you’ve worked out a new safety policy with management,” he said.