Sen. Rand Paul (R-Ky.) on Thursday signaled he would try to block President Obama’s pick for surgeon general, Vivek Murthy, because of the nominee’s political advocacy work. But new filibuster rules should allow the Senate to take a confirmation vote regardless.

In a letter to Senate Majority Leader Harry Reid (D-Nev.), Paul said he has serious concerns about Murthy’s ability to impartially serve as surgeon general because of the nominee’s past roles as a gun control proponent and advocate for Obama’s election campaigns and the Affordable Care Act.

Paul, a potential candidate for the Republican presidential ticket in 2016, has made several attempts to block the president’s nominees in recent years, placing holds on Federal Reserve board Chair Janet Yellen, FBI Director James Comey and CIA Director John Brennan before the Senate confirmed those officials.

Murthy, 36, is a doctor at Brigham and Women’s Hospital in Boston and an instructor at Harvard Medical School. He co-founded Doctors for Obama in 2008, later transforming the organization into Doctors for America, which promoted the president’s plans for an overhaul of the health-care system.

The nominee has also promoted stricter gun control, calling the issue a matter of public health. On Twitter, he once wrote: “Tired of politicians playing politics w/ guns, putting lives at risk b/c they’re scared of NRA. Guns are health care issue #debatehealth.”

“The majority of Dr. Murthy’s non-clinical experience is in political advocacy,” Paul said. “Historically, the surgeon general of the United States has been a position with the purpose of educating Americans so that they may lead healthier lives, rather than advancing a political agenda.”

At a confirmation hearing this month, Murthy said he never viewed the Affordable Care Act as a perfect solution but instead promoted it as a step in the right direction. He promised that he would focus as surgeon general on issues with broad agreement, such as preventing obesity and tobacco-related illnesses, addressing mental health problems, reducing vaccine-preventable diseases and building community partnerships to promote health at the local level.

Murthy also said his views on firearms would not come into play if he became the top U.S. doctor.

“I do not intend to use my office as surgeon general as a bully pulpit on gun control,” he said.

Under Senate rules, a unanimous voice vote can move the confirmation process to its last stage for most nominees. But with Paul’s objection, a cloture vote will have to take place before the full Senate can make a final decision about Murthy’s nomination.

Previous Senate guidelines would have required Reid to round up 60 votes to overcome filibusters and advance to the final stage, but the Senate approved new rules in November that allow the process to move forward with a simple majority voting for cloture — the old rules still apply for Supreme Court nominees.

Paul’s hold only makes the confirmation process more difficult rather than halting it.

Democrats criticized Paul for his objections Wednesday, describing his effort as a futile attempt at obstruction.

“This is just one of the many ways Republicans exploit routine matters to impose gridlock on the Senate,” said Reid spokesman Adam Jentleson.

Reid once fought to protect filibusters during the George W. Bush administration, when Democrats were blocking nominees with great frequency. This time around, Republicans have made record use of filibusters, an effort, Democrats have said, that prompted the rule change last year.