Nevada’s controversial background check ballot initiative, Question 1, claimed a narrow victory early Wednesday, despite failing in 16 of the state’s 17 counties.

Clark County voters approved the measure by a margin of 9,901 votes — out of more than 1.1 million ballots cast — making background checks mandatory for most private gun sales and transfers in Nevada.

Supporters believe Question 1 will close the “loopholes” in the federal law by preventing sales to prohibited buyers online and at gun shows, but detractors argue the backdoor attempt at a gun registry criminalizes the most trivial behaviors of law-abiding gun owners, like loaning or selling a gun to a friend, and does nothing to prevent guns from falling into the wrong hands.

The Nevada Sheriffs and Chiefs Association disavowed the ballot measure in July as unenforceable. The National Rifle Association spent $6.6 million combating the weekly ads from national gun control groups — funded largely by former New York City Mayor Michael Bloomberg, a liberal mega-donor responsible for pushing similar background check ballot measures across the country.

Nevadans for Background Checks, a Bloomberg-bankrolled state political action committee devoted to getting the ballot measure passed, touted its own law enforcement support in a flurry of ads released last month. All told, the campaign spent nearly $19.7 million pushing Question 1 before the polls closed Tuesday.

“Voters have made clear that they support common sense gun safety laws like background checks,” said Joe Duffy, campaign manager for Nevadans for Background Checks. “And now we celebrate the hard work and dedication of all of our supporters over the past year who have made this win possible.”

“This fight was in honor of all those killed by senseless gun violence and today we are one step closer to making Nevada a safer place for all of us,” said Elaine Wynn, co-chair of the Question 1 campaign. “That’s something we should all be proud of.”

A day before the polls opened Tuesday, casino mogul Steve Wynn — Elaine Wynn’s ex-husband — publicly reversed his support of Question 1, telling local media he now believed the measure’s wording too restrictive.

“I think that anytime we restrict constitutional rights of any citizen the grounds on which disqualification and being listed on a criminal registration should arbitrarily be decided by bureaucrats,” he told NBC 3 News Las Vegas.

The NRA applauded Wynn’s “stunning” turnaround and hoped it would be a “game changer” of sorts in the election.

“Like many unsuspecting Nevadans, Mr. Wynn believed the Bloomberg campaign’s false claims that Question 1 would keep guns out of the hands of criminals and make Nevadans safer,” Robert Uithoven, NRA Nevadans for Freedom campaign director, told Fox News. “Wynn went on to concede that the NRA Nevadans for Freedom is right when we say that this measure will criminalize the commonplace activities of Nevada’s law-abiding gun owners. The truth is Question 1 will not make Nevadans any safer. It will instead cost law-abiding citizens time, money, and freedom.”

Statewide polls indicated majority support for Question 1 going into Election Day, including a Las Vegas Review-Journal survey of 800 likely voters that found 54 percent would vote yes on the ballot measure versus 38 percent opposed.

G.C. Gates, editor of the Nevada Carry blog, said Wednesday the 50-49 percent vote surprised him for being “much closer” than he expected.

“Clark County lost us the vote because it has a large urban population with no tradition of shooting sports, unlike in Maine,” he said. “I think California ex-pats and Black/Hispanic minority groups also hurt us because of they tend to lean towards gun control, despite being disproportionately more affected by it. All of these factors were baked in when Everytown targeted Nevada.”

Everytown for Gun Safety, one of Bloomberg’s national gun control groups, backs background check initiatives nationwide, including Maine’s near-identical Question 3, which failed 52-48 percent Tuesday.

“Even with this loss, Everytown just found out they can’t easily knock out states in their initiative pushes,” Gates said. “More concerning is the fight we’ll have against apathetic, ill-informed gun owners and the Democrat state legislature.”