WASHINGTON -- A former national security adviser in President Barack Obama's administration plans to challenge Rep. Tom MacArthur, the New Jersey lawmaker who helped resurrect the House Republican health care plan that would leave 23 million more Americans without coverage.

Andy Kim of Marlton, a Rhodes Scholar who also advised Gen. David Petraeus in Afghanistan as a State Department official, received more than $50,000 in pledges online as he mulled whether to run.

"Health care is going to be the big issue," said Kim, 34. "He actually was the architect for reviving it and came up with the idea for gutting pre-existing condition protections that would be out of line with the district that I grew up in."

MacArthur campaign Chris Russell said the lawmaker was working to fix problems.

"Congressman MacArthur isn't in Washington to decorate a fancy chair," Russell said. "He is determined to confront and solve serious problems, including the failed Obamacare law that has caused premiums to skyrocket and decimated consumer choice."

National Republican Congressional Committee spokesman Chris Martin said Kim's tenure in the Obama White House correlated with the rise of the Islamic State.

"If that's what Kim considers a record of success, what does failure even look like?" Martin said.

MacArthur (R-3rd Dist.) is favored to win re-election by the Cook Political Report, a Washington-based publication that tracks congressional races, but rated him as more vulnerable following the health care vote. He had little trouble winning a second term last November.

The sophomore lawmaker has drawn criticism, including from constituents at a five-hour town hall meeting in May, for his role in the health care debate.

MacArthur's amendment allowed states to seek waivers from the federal requirements that insurers offer a specific package of benefits and not charge more to those with pre-existing conditions such as cancer or diabetes.

That attracted enough conservative Republicans to ensure its passage in the House, but led to his decision to resign as co-chair of the Tuesday Group of more moderate House Republicans.

The Congressional Budget Office projected that the House GOP measure would cover 23 million fewer Americans than under the Affordable Care Act, raise premiums for older patient not yet eligible for Medicare, and result in some with pre-existing conditions "unable to purchase comprehensive coverage with premiums close to those under current law and might not be able to purchase coverage at all."

The Republican bill also would cut Medicaid by $834 billion over 10 years, in part by no longer providing extra federal funding after 2019 to new enrollees in states like New Jersey that expanded coverage. Most of the savings, $664 billion, would fund tax cuts for corporations and wealthy Americans, as well as new tax breaks such as Health Savings Accounts that primarily are used by upper-income taxpayers.

"There will be be suffering and struggling because of it," Kim said. "This is going to be critically important because there are real lives on the line and real lives at stake here."

MacArthur raised $232,590 for his re-election through March 31, and just held a fundraiser with Donald Trump at the president's Bedminster golf club that brought in more than $800,000 for the congressman's re-election and state and national Republican Party committees.

MacArthur spent $5 million of his own money in the nation's most expensive open-seat congressional race in 2014, and could reach into his own pocket again.

Kim said he expected to be able to raise enough funds to compete.

"I had people all over this country pledge money, reach out to me and show me support," Kim said. "He's become a national target and, as a result, I believe we'll be able to mobilize a lot of energy all over this country to fight back against him."

Kim holds a political science degree from the University of Chicago and master's and doctorate degrees in international relations from the University of Oxford in England.

Besides his work at the White House during the Obama administration and the State Department, he worked for the Defense Department and was a Senate Foreign Relations Committee fellow under U.S. Sen. Richard Lugar (R-Ind.).

Jonathan D. Salant may be reached at jsalant@njadvancemedia.com. Follow him on Twitter @JDSalant or on Facebook. Find NJ.com Politics on Facebook.