Democrats thought they would win confirmation for more of President Obama’s nominees by waiving the 60-vote filibuster hurdle for executive branch appointments, but they didn’t factor in nervous red-state senators afraid of taking tough votes that could sink their reelection in November.

The latest apparent casualty is Vivek Murthy, a 30-something British-born American doctor, whose parents are from India, and whose Ivy League credentials and activism on public-health issues includes co-founding Doctors for America, which launched in 2008 as Doctors for Obama.

Murthy is Obama’s nominee to become surgeon general, the nation’s top doctor and a mostly ceremonial post that occupants use to highlight and elevate health issues of national concern. Testifying before Congress, Murthy said he would focus on obesity, but Republican Sen. Rand Paul believes Murthy would use the post to “propagandize” on behalf of the Affordable Care Act and against the Second Amendment.

“I doubt there’s been a surgeon general dating back to the days of Lyndon Johnson that would pass the NRA litmus test,” says Jim Kessler with the centrist Democratic group Third Way. The most famous surgeon general in modern times, Dr. C. Everett Koop, appointed by President Reagan, helped educate the country about AIDS, drew attention to the dangers of secondhand smoke, and after leaving his post wrote an editorial for the Journal of the American Medical Association in 1992 titled “Time to Bite the Bullet Back,” arguing that the right to own or operate a firearm should carry the same restrictions as car ownership.

A surgeon general’s views on gun violence have never been a litmus test before, but Murthy got the attention of the National Rifle Association with this 2012 tweet: “Tired of politicians playing politics w/ guns, putting lives at risk b/c they’re scared of NRA. Guns are a health care issue.” The NRA went public with its opposition to Murthy, and says it will “score” any vote to confirm him, meaning the organization will hold it against lawmakers, a threat that makes vulnerable Democrats get all wobbly-kneed.

The White House is now “recalibrating” what to do, and with as many as 10 Democrats poised to defect, Murthy looks like a lost cause. “The last thing they want is to take a vote that is considered anti-Second Amendment,” says an aide to Sen. Paul, who is leading the effort against Murthy. “Nobody wants to walk the electoral plank for a surgeon general,” the aide adds. “If it were a Supreme Court nominee, maybe….”

Murthy is backed by a long list of public-health-minded organizations from the American Hospital Association to the March of Dimes, and on Wednesday, the influential New England Journal of Medicine challenged what it called the NRA’s “single-issue political blackmail,” quoting a team of doctors who know Murthy personally and say they are “appalled” that a candidate of such high caliber would be taken to task for “speaking out about a problem that lands thousands of people in emergency rooms every year.”

“The critical question is this: Should a special-interest organization like the NRA have veto power over the appointment of the nation’s top doctor? The very idea is unacceptable,” the editors declare.

Unacceptable, yes, but the way politics works in Washington when you have a president with a 41 percent approval rating, and his party’s control of the Senate hanging by a thread, the better part of valor on the part of the White House is to back off, at least for now.

“This is about Rand Paul making guns a signature issue in his run for the presidency,” says Kessler, who has tracked gun issues since he worked as an aide in the Senate. He points out Paul pushed an amendment to a bill that moved through the Homeland Security and Government Affairs committee last month to allow people to carry concealed weapons into post offices. A compromise was worked out to allow concealed weapons in your car in the parking lot. “He’s out of step with some Republicans because he’s a libertarian, so he’s making a stand on guns,” says Kessler. “It’s part of his plan to win New Hampshire and South Carolina [primaries], and he’s looking for places to highlight that issue where no gun legislation has gone before.”

If Democrats are now siding with Rand Paul, it’s because the NRA has weighed in. But this may not be the last word on Vivek Murthy. “We expect this is something they will put in their hip pocket and save for the lame duck,” says Paul’s aide. “The lame duck is when you do things that are unpopular. You don’t have to worry about the electoral backlash.”

If Murthy were confirmed in the special session traditionally held after the November election and is the last hurrah for defeated and retiring lawmakers, he could still serve two years. Another nominee that might be resurrected in the same way is Debo Adebile, whose defeat in the Senate this month Obama called “a travesty.” Seven Democrats joined Republicans to reject Adebile as the nation’s top civil-rights lawyer at the Justice Department. Adebile ran afoul of nervous Democrats for his work as a lawyer for the NAACP in its representation of a cop killer in Philadelphia who is serving a life sentence without parole.