Donald Trump walked on stage at the Republican National Convention July 18 to Queen's "We Are the Champions." Trump was introducing his wife Melania who also addressed the crowd. (The Washington Post)

The Republican Party is deep in existential-crisis mode right now. It isn't just worried about Donald Trump costing Republicans the 2016 election; it's worried about him being such a disaster that he costs Republicans future elections — and even the party as it exists today.

Which brings us to George W. Bush. According to a report Tuesday by Politico's Shane Goldmacher, Bush in April mused behind closed doors that the Trump Experiment might result in him being "the last Republican president" — ever.

Via Goldmacher:

But few were as dark about the Republican Party’s future as former President Bush himself. In a more intimate moment during the [Bush administration] reunion, surrounded by a smaller clutch of former aides and advisers, Bush weighed in with an assessment so foreboding that some who relayed it could not discern if it was gallows humor or blunt realpolitik.

“I’m worried,” Bush told them, “that I will be the last Republican president.”

The comment just leaked at an inauspicious time for Republicans. Trump is set to accept their nomination Thursday, and the Never Trump movement's last gasp was Monday, when it came up short in an effort to force a full roll-call vote of delegates.

But the gloomy prediction is hardly the first of its kind. Below: a brief recap of the kind of doom and destruction some Republicans predict Donald Trump will wreak on their party.

Michael Gerson: "But Trump’s nomination would not be the temporary victory of one of the GOP’s ideological factions. It would involve the replacement of the humane ideal at the center of the party and its history. If Trump were the nominee, the GOP would cease to be."

Matthew Continetti: "The Darwin Awards is a popular website that 'commemorates individuals who protect our gene pool by making the ultimate sacrifice of their own lives. Darwin Award winners eliminate themselves in an extraordinarily idiotic manner, thereby improving our species’ chances of long-term survival.' I’d like to nominate a certain political party for one. It should win hands down."

Erick Erickson: "The beginning of the end of the Republican Party has started."

Glenn Beck: "If they put Donald Trump in, try to put him in office, if that's what the people want, you are going to see an end to the Republican Party. It will just be over, there'll just be nothing left."

Ross Douthat: "In an unhealthy system, the kind I suspect we inhabit, the Republicans will find a way to crush Trump without adapting to his message. In which case the pressure the Donald has tapped will continue to build — and when it bursts, the GOP as we know it may go with it."

David Brooks: "The leaders of the Republican Party are ... going down meekly and hoping for a quiet convention. They seem blithely unaware that this is a Joe McCarthy moment. People will be judged by where they stood at this time. Those who walked with Trump will be tainted forever after for the degradation of standards and the general election slaughter."

David Frum wrote a piece the Atlantic promoted under the headline: "Will the Republican Party Survive the 2016 Election?"

George Will: "In losing disastrously, Trump probably would create down-ballot carnage sufficient to end even Republican control of the House."

So how rooted in fact is all of this apocalyptic analysis? FiveThirtyEight's Julia Azari dug into it this week in a must-read piece:

Commentators — with either concern or glee — have noted that the Trump candidacy could spell doom for the Republican Party in the long haul. But does evidence support this?

Not really. Failed presidential candidates don’t drag their parties down as much as we might guess. Turning to recent history, the evidence of lasting impact is pretty scant. Barry Goldwater lost big in 1964, but the Republican Party rebounded and won the White House four years later. Similarly, George McGovern did much worse than the economy and other factors would have predicted in 1972, but the Democrats won the next presidential election (admittedly, with the help of Watergate). These losses also had opposite impacts on their respective parties’ ideologies. The Goldwater candidacy is credited with injecting movement conservatism into presidential politics, even though it was unsuccessful in the short term. McGovern’s candidacy, on the other hand, precipitated a move to the center, resulting in Carter’s 1976 candidacy and a general shift away from mid-20th-century liberalism.

The impact of an ideologically charged, unsuccessful presidential candidacy seems to depend on larger, long-term factors. In the 1960s and 1970s, the New Deal coalition was splintering, while the conservative movement was ascendant. This shaped how candidates like Goldwater and McGovern, who drew similar numbers in general elections, affected their parties.

Every presidential election is always the most important election in our lifetime. This is such a cliche that people who say it will often volunteer that it's a cliche while still maintaining that it's definitely still true about the next election.

And Trump has certainly unearthed a chasm in the GOP that was known about but perhaps not fully appreciated.

But everyone in politics (raising my hand here) tends to overemphasize the immediacy and effect of what's happening in the here and now. Back in 2008, some declared that Bush had killed his party. It survived.

Now, many top Republicans have made bold new predictions about the end of their party — or something close to it. Now that Trump's nomination looks as though it's a done deal, those predictions will be put to the test.

If Trump loses and it doesn't come to pass, it could just be the latest thing that the Smart People were wrong about.