Wednesday night’s two-part GOP talkathon produced some memorable exchanges among the party’s 15 candidates for president, but for my money, one of the sharpest came during the so-called junior varsity debate preceding CNN’s three-hour main event.

It was when U.S. Sen. Lindsey Graham told Gov. Bobby Jindal to grow up.

That’s not how Graham put it, of course, although his actual words were tough enough.

Jindal started the exchange when he accused Graham, and by extension, Senate Republicans, of basically refusing to blow up the place to block President Barack Obama’s Iran deal.

“I want to ask Lindsey a question. Will the Senate Republicans — they still have time — are they willing to use the nuclear option, meaning get rid of the filibusters, (to) stop Iran from becoming a nuclear power?” Jindal asked. (Senate opponents of the deal were hoping to pass a measure disapproving of the agreement, so procedurally speaking, Obama needed just 41 votes in support.)

“Now is the time for the Senate Republicans to stand up and fight,” he continued. “We are tired of the establishment saying there’s nothing we can do. All night tonight, we’ve heard Republicans say things like, ‘Well, if the Supreme Court’s ruled, there’s nothing I can do about religious liberty,’ you know. ‘The president did this. There’s nothing we can do about it for two more years.’ There is something we can do. We won the Senate. We won the House. What was the point of winning those chambers if we’re not going to do anything with them?”

Graham was having none of it, of the suggestion that the Republicans get rid of the filibuster, a tried-and-true mechanism that the party regularly uses to block actions that can’t attract 60 of 100 supporters. Nor was he willing to entertain the possibility that the GOP should shut down the government over defunding Planned Parenthood or ending the Affordable Care Act.

“So folks, the world really is the way it is,” Graham said. “President Obama is president. The goal is to get him out of there and pick somebody who would actually do something to repeal ‘Obamacare,’ who would get you a better agreement. So Bobby, he would veto the bill, we don’t have 67 votes, and you’re giving away a defense against Obama for the rest of his presidency.”

“No, I’m not going to do that. I’m not going to tell you things I can’t do. I’m not going to tell you by shutting the government down, we’re going to defund ‘Obamacare’ as long as he’s president. All that does is hurt us. I am trying to lead this party to winning,” he continued. After still more back and forth, Graham ended with this admonishment: “You know, Bobby, we’re running to be president of the United States, the most important job in the free world. With it comes a certain amount of honesty. I’m tired of telling people things they want to hear that I know we can’t do.”

This wasn’t just an academic discussion, of course, but a distillation of one of the main running fights within the party.

Graham is a 20-year veteran of Congress and a respected establishment figure, even if nobody’s taking his presidential aspirations seriously. His low poll numbers landed him in the preliminary round, alongside Jindal, former Pennsylvania U.S. Sen. Rick Santorum and former New York Gov. George Pataki.

Unlike Graham, who’s campaigning like someone with nothing to lose, Jindal’s still nursing the hope that he’ll make it to the big stage one day, just as Carly Fiorina did after the last two-tiered debate. One way he’s trying to sell himself is as an outsider, just like Donald Trump, Ben Carson and Fiorina — not to mention actual elected officials such as Ted Cruz, the Texas senator and de facto leader of the shut-the-place-down caucus.

But Graham’s right. As a former congressman who spent his career in various state and local posts before entering politics and eventually becoming governor, Jindal knows better. He knows how the division of powers works, he knows what powers Congress has relative to the president, and he knows that the Supreme Court is the ultimate arbiter of constitutional rights and the law of the land.

Of course, the exchange was as much as about politics as about policy. As Graham noted, GOP absolutism is off-putting to swing voters who expect government to function, and it could cost the Republicans the general election — although it’s true that Jindal’s stance may well be more popular with the party’s primary voters.

But Jindal’s got two problems here. Based on his background, he’s not much of a messenger for the cause. And the message itself undermines whatever credibility he hopes to tap into as someone who claims to be serious about governing. And Graham’s right. Jindal is both smart enough and experienced enough to know it.

Stephanie Grace can be contacted at sgrace@theadvocate.com. Read her blog at http://blogs.theadvocate.com/gracenotes. Follow her on Twitter, @stephgracenola.