Sen. Ted Cruz (R-Tex.) works on his pitch.

At a cattle call for prospective presidential candidates on Capitol Hill Tuesday, Republican hopefuls couldn’t say enough good things about the members of one powerful public sector union: the firefighters.

"God bless firefighters,” said Sen. Ted Cruz (R-Tex.), gazing out upon a sea of burly first responders seated at long tables in a hotel ballroom. “I am in awe to be in the presence of heroes.”

“Firefighters embody the best values of our nation: service, commitment, dedication and unapologetic patriotism,” said the video feed of former Florida governor Jeb Bush, who couldn’t make the International Association of Firefighters’ annual legislative conference but took the time to record a greeting.

“I’m looking at the guys who run into burning buildings,” said Sen. Lindsey O. Graham (R- S.C.), "and I’d be the first one to run out.” Rep. Pete T. King (R-N.Y.), Sen. Marco Rubio (R-Fla.) and former New York governor George Pataki rounded out the morning on the GOP side.

Despite the praise, though, the affection was largely not returned. Jokes at Hillary Rodham Clinton’s expense fell flat, and saber rattling over Iran elicited little response, as did typical conservative arguments about getting government out of the way — as a firefighter, you might reasonably ask whether they had your interests at heart.

“I enjoyed the Democrats, not so much the Republicans,” said John Daum, a firefighter in Greenwich, Conn. “I don’t think they support labor.”

Now, Republicans don’t usually bother trying to seek support from labor unions, which lean heavily Democratic. Most unions couldn’t have summoned that list of busy conservatives to make a customized pitch to their members — let alone to an audience of government employees, who have come squarely into the sights of GOP politicians from the federal level on down.

[Webb, O’Malley seek support among firefighters]

But firefighters are a special breed of union, serving as symbols of strength and valor — a helpful backdrop for politicians seeking to wrap themselves in the flag. They’re a relatively conservative bunch, with 44 percent of their 300,000 members identifying as Republican. (According to a Gallup poll from 2011, only 26.6 percent of unionized local government employees are Republican.) Sometimes they even endorse Republicans, as the Florida firefighters did in 2004 for George W. Bush. And they've got a reputation for working with both parties to get things they want, like more Homeland Security funding for local fire departments (sometimes at the expense of efficiency, in the light of firefighters’ changing role in cities).

“We know that there are many in that arena who appreciate the work that we do,” said IAFF President Harold Schaitberger, speaking of the Republicans while killing time in between speeches. And the union is as muscular financially as it is physically. Schaitberger boasted that the firefighters’ PAC was the 34th largest in the nation, having handed out $6.4 million in 2014 — mostly to Democrats but occasionally to Republicans too.

Accordingly, firefighters are sometimes even protected from legislation that damages other unions. Michigan, for example, exempted firefighters and police from its 2012 right-to-work law. Illinois Gov. Bruce Rauner (R), who showered criticism on public sector unions during his campaign, proposed cutting a “special deal” to preserve police and firefighter pensions.

But if Republicans are interested in the firefighters’ support, they had little to offer in the way of things they actually care about. While several talked about the problems of inequality and a failing middle class, most simply offered growth as a solution, rather than empowering the labor movement. Cruz, who has a zero percent rating on the AFL-CIO’s annual voting scorecard, tried to make common cause with the firefighters over their dissatisfaction with the “Cadillac Tax” on their health-care plans under Obamacare — and drew a swift rebuttal.

"Ted Cruz seemed to struggle up there,” remarked Scott Mullins, a firefighter from Asheville, N.C. "He seemed a little awkward."

The event avoided the worst potential awkwardness, though, given that GOP presidential contenders who have really antagonized the firefighters weren’t present: Gov. Scott Walker, who just signed a right-to-work bill in Wisconsin, declined an invitation. New Jersey Gov. Chris Christie, who is still trying to slash public employee pensions after being dealt a setback in the courts, wasn’t invited at all.

[Jeb Bush, Scott Walker emerging as front-runners for GOP nod — and rivals]

King and Graham fared a little better, with King hitting Republicans like Cruz, who had held up funding for the Department of Homeland Security because of its immigration provisions. But the biggest applause line of the morning came at the end, from former Maryland governor Martin O’Malley (D), who had the advantage of critiquing politicians who spoke earlier in the event.

"All of the Republican leaders you heard from today are opposed to collective bargaining, because collective bargaining runs counter to their belief that keeping wages low somehow makes America’s economy better,” he said, to a standing ovation. And then, he put his finger on the sense of discomfort firefighters had with the conservative leaders who took the stage before him.

“When someone dials 911, and you show up to run into a burning building, have you ever once had a citizen say, 'No thanks, I believe government is the problem’?”

O’Malley’s broadsides resonated especially with the North Carolina firefighters, who live in one of the four states where collective bargaining is illegal for firefighters. Partly as a result, their median hourly wage is a full $6 below the nationwide average.

“O’Malley definitely struck a chord with us,” said Thomas Brewer, from Charlotte.