Republicans on Tuesday trumpeted what they view as a second fatal blow to Obamacare, the president’s signature legislative achievement, after the revelation that the Obama administration had delayed until 2015 the law’s cap on out-of-pocket costs for medical care.

“First, it was Christmas — and now it’s our birthday,” said a giddy senior House GOP leadership aide.

GOP leaders were already getting traction from the Obama administration’s decision to delay until 2015 the mandate requiring larger employers to purchase health insurance for their employees.

With the health care overhaul’s delay on limits for out-of-pocket costs, Americans will continue to pay more than promised for their health care, undermining Obama’s call for more affordable coverage.

The latest argument from Republicans, who have voted 40 times to defund or repeal portions of Obamacare: Which of the president’s health care promises have gone as planned?

And House leaders are trying to stoke the charge that Obama is looking out for special interests at the expense of ordinary Americans who will still be forced to buy insurance through the individual mandate.

“Once again the president is giving a break to big businesses struggling with his health care law while individuals and families unfairly remain stuck under its mandates,” said House Speaker John Boehner. “This report is just the latest evidence that the law is too costly and too complex to work — and that it’s not being implemented fairly.”

The administrative change was approved in February, but was only recently discovered in a cryptic online explanation of the new law on the Labor Department’s website.

The implementation of the Affordable Care Act will certainly hang over the 2014 mid-term elections. Aware of the major political liability, senior Obama administration officials have repeatedly reached out to skittish Democrats to convince them the health reforms won’t doom their re-election chances.

A growing number of Americans, including Democrats, are souring on the president’s health care reforms, a series of recent polls found.

But Democrats are starting to get more aggressive in their defense of Obamacare. On Tuesday, the Democratic Congressional Campaign Committee targeted 60 House Republicans who pushed for repeal of the law.

For example, the liberal group ripped Rep. Gary Miller, R-Calif., among others opposed to Obamacare.

“Americans want their premiums to go toward benefits,” the DCCC said in a release targeting his district, “but Congressman Miller would rather go back to the dark days when insurance companies spent the hardworking California families’ money on bigger bonuses and higher administrative costs.”