Intense opposition from the National Rifle Association has all but doomed prospects for President Obama’s nominee for surgeon general, as pro-gun Senate Democrats peeled away from the White House on a volatile issue in an election year.

Facing a potential high-profile setback for the president, the White House is not pushing for a vote to confirm Dr. Vivek Hallegere Murthy, a Harvard- and Yale-educated internist and former emergency room doctor who has advocated for stricter gun control laws, Senate aides said.

Democratic leaders in the Senate have begun surveying senators to determine whether there is enough support to save the troubled nomination. Few Republicans are expected to back Murthy, and as many as eight Democrats also could be opposed.

“We don’t expect a vote to happen,” a Senate aide said.

The divide between the White House and the ­president’s party has widened in recent weeks as Obama’s low poll numbers leave Democrats increasingly concerned about their chances in the November midterm election.

Earlier this month, Obama’s nominee to head the Justice Department’s civil rights division, Debo Adegbile, was rejected by the full Senate after several Democrats joined Republicans in opposing him.

Gun rights issues are particularly powerful in an election year, and the entrance of the NRA into the surgeon general confirmation opens a new front in the gun lobby’s efforts to halt any attempts at federal firearms restrictions.

In the past, the NRA didn’t venture into nomination battles beyond those directly related to Second Amendment issues.

A spokesman for the NRA said Saturday that the organization was simply responding to the White House decision to nominate a gun control advocate.

“We’re forced to get involved and voice our opposition,” said NRA spokesman Andrew Arulanandam.