The Bush family, a dynasty that defined Republicanism for decades, clashed on Monday with the new and irreverent face of the party, Donald J. Trump, in one of the most vivid and powerful confrontations in the presidential primary campaign so far.

Jeb Bush, facing increasing pressure in South Carolina after lackluster showings in early contests, brought his older brother, George W. Bush, and the former first lady, Laura Bush, to vouch for his decency and judgment here in a race that has been driven in recent weeks by coarse language, anger and personal insults.Mr. Bush also praised his younger brother's "deep and genuine faith" — "faith that reveals itself through good works, not loud words," he said — and argued for nominating a Republican who can win the general election in November.

"There seems to be a lot of name-calling going on, but I want to remind you what our good dad told me one time — labels are for soup cans," the former president told a crowd that the campaign estimated at 3,000 people at a civic center here. "The presidency is a serious job that requires sound judgment and good ideas, and there's no doubt in my mind that Jeb Bush has the experience and the character to be a great president."

Mr. Bush also praised his younger brother's "deep and genuine faith" — "faith that reveals itself through good works, not loud words," he said — and argued for nominating a Republican who can win the general election in November. "All the sloganeering and all the talk doesn't matter if we don't win," he said. "These are tough times, and I understand that Americans are angry and frustrated, but we do not need someone in the Oval Office who mirrors and inflames our anger and frustration."

The former president spoke hours after Mr. Trump, who has been leading in polls here, held a news conference nearby in which he continued his assault on Mr. Bush, mocking his famous "Mission Accomplished" appearance during the Iraq war and pointedly saying the country was not "safe" during the president's tenure.

"What does that mean, he kept the country safe after 9/11?" Mr. Trump asked, repeating a broadside — that the 43rd president was responsible for the terrorist attacks of Sept. 11, 2001 — that he used in Saturday's Republican debate. "What about during 9/11? I was there."

Growing sharper as he spoke, Mr. Trump continued: "The worst attack ever in this country? It was during his presidency." He added that praising the former president for what happened after the Sept. 11 attacks was like saying the opposing team "scored 19 runs in the first inning, but after that, we played pretty well." Mr. Trump's pointed critique of President Bush's performance on terrorism has startled some of the conservative world's leaders and opinion makers, like Rush Limbaugh, who likened Mr. Trump to the leftist filmmaker Michael Moore — a comparison Jeb Bush also made at the rally. Such attacks on the most recent Republican president are unheard-of among the leading Republican candidates, and it is difficult to predict how they will affect the Saturday primary in South Carolina, where the Bush presidencies, and family, are remembered fondly. But Mr. Trump's words may have affected the former president, who spent much of his 30-minute speech defending his administration and his personal response to the Sept. 11 attacks, even starting at the elementary school in Florida where he first learned that planes had crashed into the World Trade Center's twin towers. More from The New York Times : A New Culprit in Lyme Disease

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'A Mother's Reckoning,' by Sue Klebold "On the way to Air Force One, from that school, Condi called me and said a plane has hit the Pentagon," the former president said, referring to Condoleezza Rice, his national security adviser at the time. "I felt the first one was an accident, the second was an attack, and the third one was a declaration of war. I became something that no president should ever want to be — a wartime president." Mr. Trump's news conference, several miles north of here, offered a striking contrast with the Bush family rally on Monday evening. Mr. Trump, in a freewheeling, sometimes stream-of-consciousness style, spoke for more than 45 minutes, criticizing — and even threatening to sue — his rivals, squinting angrily at times and dismissing questions he did not like.

Jeb Bush and his older brother, meanwhile, offered the waving, smiling feel of a reunion tour — both a look back to the Bush administration, and a look ahead to why the younger brother, whom George W. Bush introduced to cheers as "my big little brother," is the right choice for the future of the country. Though the tone of the rally was serious and at times somber, especially when the former president discussed the Sept. 11 attacks, he also cracked jokes. Looking older — his hairline a bit farther back, his face longer — he seemed to relish his time before the friendly crowd. "I've written two books, which has surprised a lot of people, particularly up East, who didn't think I could read, much less write," the former president said. "I've been one to defy expectations. I've been misunderestimated most of my life. And as a real shock to people, I've become an oil painter. But let me assure you I know that the signature is worth more than the painting." He also offered loving recollections of being at the White House during his father's term, and being chided by his mother, Barbara Bush, for putting his feet on the Jeffersonian table. The day seemed to crystallize how flummoxed the Republican establishment has become over Mr. Trump, and his rule-breaking, unorthodox and broadly appealing campaign for president. Mr. Trump's wide-ranging comments pre-empted what would have been warmhearted and respectful footage of the former president meeting with veterans here. Mr. Trump, during his news conference, said bluntly that the United States should not have gotten rid of Saddam Hussein in Iraq. "Now Iraq is Harvard for terrorism," he said. "You want to become a terrorist? You go to Iraq. Saddam Hussein understood, and he killed terrorists."