WASHINGTON -- Republicans in the House of Representatives have been trying to repeal the Affordable Care Act for years. Now, with Democrats no longer in control of the Senate, the GOP is attacking the health care law with renewed vigor.

But their first attempt of the new year -- to be voted on in the House on Thursday -- isn’t likely to get very far.  Republicans will quickly move a bill through Congress to change a provision in the ACA that defines how long an employee must work each week to be considered full time, and therefore qualify for health insurance. The current law sets the threshold at 30 hours. Republicans, who argue the standard is hurting American workers, want to raise the definition of full time to 40 hours. President Barack Obama already has said he will veto the legislation.

As a result, one of the first bills passed by the Republican-controlled Congress is likely to be short-lived. But the fallout will undoubtedly linger, creating a new GOP talking point that Democrats are killing jobs and damaging the economy. And Democrats will make the most of it with their own talk-show topics, accusing Republicans of putting corporate bottom lines ahead of access to affordable health care.

Republicans know they can't repeal Obamacare in its entirety. Obama would never sign it. Plus, the law is too far into implementation for Republicans to wipe the slate clean without offering an alternative. Such a move would mean ending subsidies and access to coverage for millions of people.

Instead, Obamacare’s opponents would like to whittle away at the law. The first goal is to pressure congressional Democrats to back eliminating pieces of the law that have strong bipartisan and public support and develop veto-proof majorities. If that doesn't work, Republicans will focus on the elements of the law that draw strong public outrage and try to build strong opposition to tout in the next election. The 30-hour workweek provision is one such part of the ACA because the message of jobs resonates with voters. And while in no way does the law say people can't or shouldn't work 40 hours, Republicans are casting it as an assault on full-time employment.

"One of the worst things we can do is destroy the 40-hour workweek, which has been a part of American culture and life for a very long time," Senate Minority Leader Mitch McConnell said on Wednesday. "It is wreaking havoc out in society."

The support for changing the ACA is coming from business entities like the U.S. Chamber of Commerce and trade groups the National Restaurant Association and the National Retail Federation. Those trade groups represent big employers, such as Walmart and McDonald's. But their member companies are leaving the lobbying to industry organizations.

In a sign that the legislation is likely more about politics than policy, private businesses don’t appear to be putting in a lot of effort and aren’t making an aggressive sell on the Hill to try to round up enough Democrats to produce veto-proof margins.

In crafting the Affordable Care Act, the law defined employees who work more than 30 hours a week as full time. For large, national companies with more than 100 employees like retail chains, employers are now required to provide insurance for full-time employees or faces penalties. Beginning in 2016, smaller companies with 50 full-time employees will also be subject to the same rule. Republicans want to redefine full time to 40 hours, making it easier for more companies to skirt the insurance requirements.

One need not look any farther than the name of the bill -- the Save American Workers Act -- to understand that Republicans are making the change about jobs and not health care. Supporters of the changes to the ACA argue that part-time workers would be able to work more hours without burdening their employer with insurance costs.

Neil Trautwein, National Retail Federation vice president for health care policy, said while his organization would prefer Congress had never set a threshold for coverage -- essentially meaning no employer mandate -- he thinks it’s “within Congress’ wheelhouse” to set the requirement at 40 hours.

Trade groups argue their members may be forced to cut hours for their employees if the regulations aren't changed. The status quo is “going to encourage employers, retailers and others in the economy with 100 or more employees to hold hourly workers below 30 hours, say 29 hours, in order to manage their potential liability and cost under the Affordable Care Act,” Trautwein said.

James Sherk, senior policy analyst in labor economics at the conservative Heritage Foundation, said the cost of the regulation is burdensome on businesses. The penalty for not providing health coverage as the law requires comes to $2,000 pretax dollars per employee, which would translate to $3,400 in payroll costs. “It’s the equivalent of having to give every one of their employees a $3,400 bonus if they want to hire them full time, and of course the bonus doesn’t go to the employee, it goes to the federal government,” Sherk said.

Katie Mahoney, executive director of health policy for the U.S. Chamber of Commerce, said her organization and several other trade groups have launched a coalition that takes the position that changing the requirement will grow paychecks for those who would like to work more hours but remain part time. The group sent letters to House and Senate leadership on Wednesday signed by state and local trade associations.

“What we’re expecting we will see if this does not change is a world in which more people will have to work more than one job, and not because they want to ... simply because they’re not able to work the number of hours for one employer they would otherwise be able to.”

There is a growing amount of opposition to the proposal. For starters, the numbers aren't looking good for Republicans based on scores released Wednesday by the Congressional Budget Office. The nonpartisan CBO estimated that because the change would reduce penalties, cause more people to lose their health insurance and drive up the need for subsidized coverage, the Republican proposal would increase the deficit by  $18.1 billion over the 2015-2020 period and by $53.2 billion over the 2015-2025 period. For Republicans who have been insistent that legislation be paid for, this could cause a wrinkle in the effort to quickly move the legislation.

The CBO also estimates 1 million people would be dropped from their employer health insurance. As a result, the CBO says, there would be an additional 500,000 uninsured Americans. 

“It would significantly increase the deficit, reduce the number of Americans with employer-based health insurance coverage, and create incentives for employers to shift their employees to part-time work – causing the problem it intends to solve,” the White House argued in a veto threat. “Rather than attempting once again to repeal or undermine the Affordable Care Act, which the House has tried to do over 50 times, it is time for the Congress to stop fighting old political battles and join the president in forwarding an agenda focused on providing greater economic opportunity and security for middle-class families and all those working to be a part of the middle class.”

And there is a growing conservative opposition to changing the rules, mostly from people who would rather see the law done away with entirely.

Sherk points out changing the threshold could result in even more workers' hours being cut. “It creates a new problem by encouraging companies to make modest cuts to hours,” he said – for example, cutting employee hours from 40 to 39 to evade a full-time definition.

Indeed, a study last year by the nonpartisan Commonwealth Fund found that raising the threshold to 40 hours, compared with the 30-hour definition, would put “more than twice as many workers at high risk of hours reductions.” That’s because the majority (51 percent) of year-round workers at firms with 50 employees or more work between 40 and 44 hours a week. And about 9 percent, or 2.6 million, of those workers aren’t currently offered employer-sponsored health coverage.

Sherk said the better fix “would be to get rid of the employer mandate,” rather than raise it to a higher threshold.