Donald Trump’s candidacy has driven away throngs of Republican elected officials, donors and policy experts. But not the National Rifle Association.

With Trump increasingly isolated and hobbled by controversies of his own making, the powerful gun-rights group has emerged as one of his remaining stalwart allies in the Republican coalition: The institution on the right most aggressively committed to his candidacy, except for the Republican National Committee itself.

The association has spent millions of dollars on television commercials for Trump, even as other Republican groups have kept their checkbooks closed and Trump’s campaign has not run any ads of its own. The NRA’s chief political strategist, Chris Cox, gave a forceful testimonial for Trump at the Republican convention; Trump has repeatedly praised Cox and the association’s executive vice president, Wayne LaPierre.

And on Tuesday, when Trump roiled the presidential race anew with a rough comment — his critics interpreted it as a suggestion that “Second Amendment people” could attack Hillary Clinton or the judges she would appoint if elected president — the association rushed to defend his remark as no more than an attempt to rally gun enthusiasts to vote in November.

Allies of Trump and the association describe their political alliance as a marriage forged out of urgent necessity: an unlikely pairing of a former gun-control proponent who lives in a Manhattan skyscraper with an advocacy group typically seen as speaking for gun manufacturers and the hunters and sportsmen of Middle America.

But Trump has effectively romanced the pro-gun community with a message of fierce support for Second Amendment rights. And the NRA, spurred by concern about Clinton’s power to name Supreme Court judges, has reciprocated his overtures with enthusiasm.

Helping to establish that connection have been Trump’s sons, Donald Jr. and Eric, avid hunters with ties to the NRA. Donald Jr., Trump’s oldest son, spoke about the importance of gun rights on a visit to Capitol Hill in the spring.

On the campaign trail, Trump makes a show of embracing the association and its leadership, while accusing Clinton of seeking to do away with the Second Amendment.

“We’re going to help the NRA, who are great people,” he said Tuesday in Fayetteville, N.C. “They’re fighting hard, they’re fighting hard. Chris and Wayne and all their people at the NRA, these are people that love our country.”

The alliance with Trump comes at a moment of peril for the NRA and its agenda, as Democrats threaten to take control of the Senate and polls show the public increasingly supportive of at least modest new limits on the sale and possession of firearms.

Clinton and other Democrats have run explicitly against the NRA in this election, attacking the gun lobby for opposing laws intended to restrict gun sales to people with mental illnesses or whose names are on the federal terrorism watch list. They have held up the NRA as a uniquely sinister organization, and cast themselves as opponents of the group rather than of gun owners in general.

In her acceptance speech at the Democratic convention last month, Clinton said the country could not have a president “in the pocket of the gun lobby.”

“I’m not here to repeal the Second Amendment,” she told the crowd in Philadelphia. “I’m not here to take away your guns. I just don’t want you to be shot by someone who shouldn’t have a gun in the first place.”

Clinton, who has campaigned with gun-control advocates like former congresswoman Gabrielle Giffords and her husband, Mark Kelly, told a crowd in Iowa on Wednesday that Trump’s provocative remark about Second Amendment supporters showed he was unfit to be president. She called it “the latest in a long line of casual comments from Donald Trump that cross the line.”

The NRA is expected to intensify its efforts on Trump’s behalf, association officials said, increasing its spending on television commercials and wielding its extensive network of activists to help turn out voters sympathetic to Trump.

The NRA has spent nearly $6 million this year on advertising supporting Trump, focusing its latest efforts on the swing states of Nevada, North Carolina, Ohio and Pennsylvania, where Trump and his running mate, Gov. Mike Pence of Indiana, have been campaigning heavily. That sum — a tiny fraction of what has been spent on commercials backing Clinton — is the largest expenditure for ads helping Trump in the general election.

At this point in the last two presidential elections, the NRA had not spent a single dollar on commercials backing the Republican nominees, John McCain in 2008 and Mitt Romney in 2012, according to the ad tracking firm Kantar Media/CMAG. In 2004, the rifle association spent just $61,000 aiding President George W. Bush’s re-election bid, and only in Washington.

Grover Norquist, an anti-tax activist who sits on the rifle association’s board, said the 2016 race was uniquely explosive because control of the Supreme Court hangs in the balance and Clinton has spoken critically of judicial decisions that take a broad interpretation of the right to own guns.

“Trump in his public statements, in his speech at the convention, is the most pro-Second Amendment presidential candidate of either party in living memory,” Norquist said. “And we haven’t had a presidential candidate declare war on the Second Amendment community as aggressively as Hillary.”

Norquist said that the NRA and other Second Amendment groups were determined to reach voters who are concerned about crime and self-defense, and who might hold permits to carry concealed weapons but were not recreational gun users like hunters and sportsmen. Those voters may not fit the conventional profile of gun owners, he said, and may be more likely to live in battleground states like Florida, Michigan and Pennsylvania.

“They are more suburban,” Norquist said. “They are more likely to be swing voters and not necessarily NRA members.”

The NRA’s ads have focused on themes of self-defense and fear — and on persuading gun owners that they should fear Clinton: Its latest commercial, released Tuesday, accused her of hypocrisy for surrounding herself with armed guards while trying to take away Americans’ firearms, leaving them “defenseless.”

At times, the association has taken its advocacy for Trump well beyond gun rights. With no well-funded super PAC running ads for Trump, the NRA stepped into that role in late June, releasing an ad on an entirely unrelated issue. The commercial featured a survivor of the 2012 attack in Benghazi, Libya, criticizing Clinton’s handling of it. It made no mention of guns or any other domestic policy issue.

And the NRA has used its digital channels, which reach more than 5 million members, to echo Trump’s messages: Ginny Simone, a reporter for NRA News, the association’s online channel, recently offered a glowing video package showcasing Trump’s convention speech and trumpeting his support among gun owners.

sTrump has not always been such a clear ally of the gun lobby. When he considered a bid for president in 2000, he repeatedly expressed support for a crackdown on gun ownership, and criticized Republicans who, he said, “walk the NRA line and refuse even limited restrictions.”

But this year, Trump has gone to unusual lengths to get along with the organization. When the group offered rare criticism of him in June, for suggesting after the nightclub massacre in Orlando, Fla., that patrons there should have been armed, Trump took the unusual step of walking back his remarks.

His intention, he insisted, had been to suggest that more armed guards at the nightclub would have been helpful.

© 2016 The New York Times Company