Donald Trump had always described his run for president as unique. Going it alone without support from senior leaders of the Republican Party may just be another thing that sets him apart.

“Does it have to be unified? I’m very different than everybody else, perhaps, that’s ever run for office. I actually don’t think so,” Trump told George Stephanopoulos on ABC News’ “This Week” on Sunday.

A growing roster of Republicans have said they won’t back their party’s presumptive nominee in November, including former Florida Gov. Jeb Bush, who competed against Trump this year, and Mitt Romney, the 2012 Republican nominee. On Sunday, the 2008 nominee, Arizona Sen. John McCain, said “a lot of things would have to happen” before he’d campaign for Trump.

While that hasn’t rattled Trump, he sounded disappointed after House Speaker Paul Ryan wasn’t ready to back the real-estate developer and television personality who’s dominated the Republican primaries. “I was blindsided a little bit, because he spoke to me three weeks ago, and it was a very nice call, a very encouraging call,” Trump said on NBC’s “Meet the Press.”

Ryan told CNN on May 5 that Trump needed to stop the bullying and demonstrate his conservative credentials. “I hope to support our nominee,” the Wisconsin representative said. “At this point, I’m just not there.”

Ryan’s remarks were a sign of how much Trump needs to do to bring Republicans along with him after a divisive and bruising primary season. Trump’s final opponents, Texas Sen. Ted Cruz and Ohio Gov. John Kasich, bowed out after the May 3 Indiana primary, where Trump captured 53 percent of the vote.

Asked on NBC if Ryan should still chair the Republican National Convention in Cleveland in July if he continues to withhold support, Trump punted: “I will give you a very solid answer, if that happens, about one minute after that happens.”

Former Alaska Gov. Sarah Palin told CNN’s “State of the Union” on Sunday that Ryan’s political career “is over but for a miracle” after he “disrespected” the more than 10 million Republican voters who’ve supported Trump.

Ryan may soon be “Cantored,” said Palin, in a reference to former Virginia Rep. Eric Cantor, considered to be the front-runner to become House speaker before he lost his primary election in 2014 to an unheralded college professor.

While some Republicans in Congress reject Trump, other current and former lawmakers have said they will back the reality TV star as the nominee -- if nothing else, than to block Democrat Hillary Clinton’s path to the White House.

“I think it would be better if it were unified, I think it would be -- there would be something good about it,” Trump told ABC, referring to the Republican Party. “But I don’t think it actually has to be unified in the traditional sense.”

Trump’s rise has been fueled by dissatisfied Americans who’ve lost their jobs, and young people saddled with debts, and the party needs to take heed, McCain said on CNN’s “State of the Union” on Sunday. “You have to listen to people who have chosen the nominee,” McCain said.

Still, he called on Trump to apologize for belittling comments made in 2015. Campaigning in Iowa in July, Trump said McCain, a naval aviator shot down during the Vietnam War and held as a prisoner of war for five years, was “not a war hero.”

“It’s important for Donald Trump to express his appreciation for veterans -- not John McCain, but veterans who were incarcerated as prisoners of war,” McCain said.

Pivoting to his likely general election opponent, Trump told ABC that bringing up Bill Clinton is “fair game” because he’s involved in Hillary Clinton’s campaign, though the offensive treatment of spouses like his own wife, Melania, is “unfair.”

At rallies over the weekend Trump linked the Democratic front-runner with husband Bill Clinton’s past marital infidelities and 1998 impeachment. “She’s married to a man who was the worst abuser of women in the history of politics,” he said in Spokane, Washington, on Saturday. “Hillary was an enabler and she treated these women horribly.”

“He was impeached for lying about what happened with a woman, and she’s going to take ads about little Donald Trump?” Trump said, referring to the Clintons. “I don’t think so.”

Groups supporting Clinton have reserved millions of dollars in television advertising that’s expected to focus on the Republican’s past demeaning statements about women.