UPDATED: 5:20 p.m. | The Obama administration’s stunning punt on the employer mandate in the health care law will be a major focus of House Republicans when they return next week.

Republicans believe the decision gives them a chance to go on offense.

“It’s obvious they did this while the president was in the air in the middle of a holiday week to minimize the coverage of this breathtakingly significant development,” said one senior Republican leadership aide of the timing of the announcement. “It builds momentum and support for repealing the entire law [and] I’m sure that the impact … will be a huge topic next week.”

Lawmakers also are busy launching investigations into the decision and its legality.

House Energy and Commerce Committee Chairman Fred Upton, R-Mich., is launching a formal investigation into what he characterized as an “abrupt” decision to delay implementation of the employer mandate. He is requesting documents from Treasury Secretary Jack Lew and Health and Human Services Secretary Kathleen Sebelius that shed light on how and why this decision was made.

“Despite delays and missed deadlines, administration officials had repeatedly testified before Congress that they were still on schedule to implement the law. Yesterday, they admitted that wasn’t the case, and it’s clear we have no idea the full scope of delays and disarray that may be coming. The American public deserves answers,” said Upton in a statement.

Upton has given Lew and Sebelius a July 17 deadline to turn in “information regarding the individuals, companies and organizations the administration was consulting with regarding the employer mandate and other provisions that may be delayed or modified.” The committee’s press release also indicated that the Subcommittee on Oversight and Investigations will “examine the administration’s delay of the employer mandate in the coming weeks.”

Oversight and Government Reform Chairman Darrell Issa, R-Calif., and Rep. Phil Roe, R-Tenn., also have questioned whether the White House even has the authority to delay implementation of the employer-offered insurance mandate without congressional consent.

And Rep. Joe Pitts, R-Pa., wants Sebelius to come back and testify before the Energy and Commerce Subcommittee on Health, of which he is the chairman.

“When Secretary Sebelius was before my Health Subcommittee, she insisted everything would start on time. I wonder how many other surprises we are in for before the end of the year? She should come back to the committee and be open and honest with us about how the implementation of law is going,” Pitts said in a statement Wednesday.

Republicans have already passed a full repeal of the law, and GOP leaders indicated they would continue that push.

Amanda Austin, director of federal policy for the National Federation of Independent Business that opposes the health law, said that above all else, Congress must be realistic in how it chooses to respond.

“[The House has] had a number of votes on full repeal and obviously the Senate has gone nowhere with it,” Austin told CQ Roll Call on Wednesday morning. “Like business owners, we need to be practical about what we can get done. We are inching closer and closer to more of this law going into place.”

Austin said NFIB’s big focus right now is urging lawmakers to act on a bill introduced in the Senate by Susan Collins, R-Maine, and Joe Donnelly, D-Ind., that would define a full-time employee as one who works 40 hours a week; the new health law defines a full-time employee as one who works at least 30 hours. The bipartisan support of the legislation could be significant, she said. It might possibly be something that could pass in the Senate and get considered in the House.

But one House Democratic aide said he didn’t expect Republicans to be able to do much more than message on the most recent delay.

“They are absolutely desperate to do anything to undermine this law, whether it’s discouraging people, whether it’s holding more hearings, everything short of ripping an enrollment form out of someone’s hand,” the aide said.

Democratic leaders, meanwhile, sought to put the best spin they could on the announcement, which came more than three years after the enactment of the law.

“With this announcement, the Administration has demonstrated its commitment to implement the Affordable Care Act with increased flexibility for the four percent of America’s businesses impacted by the employer responsibility requirement,” House Minority Leader Nancy Pelosi, D-Calif., said in a statement Wednesday that fell in line with much of the rhetoric used so far by the White House and high-ranking Democratic officials.