When The Post's front page declares: "Republicans are on the verge of ceasing to function as a national party," it's time to ask: How did this come to pass? You can choose from a litany of insurrections, government shutdowns and other self-inflicted wounds. But this year's carnival-like GOP presidential primary makes one event, in retrospect, stand out as a crucial turning point on the road to upheaval: the 2008 embrace of then-Alaska Gov. Sarah Palin to be a heartbeat from the presidency.

Palin's blatant lack of competence and preparedness needs no belaboring. What's critical is that substantive, serious Republican leaders either wouldn't or couldn't declare, before or after the election: "This is not what our party stands for. We can and must do better." By the campaign's end, GOP operatives were shielding Palin from even the simplest questions. (She had flunked "what newspapers do you read?"). Barack Obama cruised to victory.

Palin became a Fox News fixture, reinforcing the newly formed tea party's "never compromise" demands. Bombast, not reason, reigned. Now the "settle for flash" aura of Palin's candidacy looks like a warning that the party was prizing glib, red-meat rhetoric over reasoned solutions.

Sadly, Palin owes her fame to 2008 presidential nominee John McCain, who is generally one of the party's more thoughtful and substantive veterans. He has championed reforms to immigration and campaign finance. He denounced "wacko birds" who stymie Congress to pursue hard-right agendas with no chance of passage. Whether McCain actively sought Palin in 2008 or passively yielded to aides' pressure, he set a new standard for GOP candidates who rely on lots of sizzle and little substance.

Once McCain put Palin on the ticket, Republican "grown-ups," who presumably knew better, had to bite their tongues. But after the election, when they were free to speak their minds, they either remained quiet or abetted the dumbing-down of the party.

They stood by as Donald Trump and others noisily pushed claims that Obama was born in Kenya. And they gladly rode the tea party tiger to sweeping victories in 2010 and 2014.

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Now that tiger is devouring the GOP establishment. Party elders had hoped new presidential debate rules would give them greater control. But they are watching helplessly as Trump leads the pack and House Republicans engage in fratricide.

It's hard to feel much sympathy. The Republican establishment's 2008 embrace of Palin set an irresponsibly low bar. Coincidence or not, a batch of nonsense-spewing, hard-right candidates quickly followed, often to disastrous effect.

In Delaware, the utterly unprepared Christine O'Donnell promised "I'm not a witch," but it didn't save a Senate seat that popular, centrist Republican representative Mike Castle would have won, had he been the nominee.

In 2012, Missouri Republicans hoped to oust Sen. Claire McCaskill (D). Those hopes died when GOP nominee Todd Akin opined that "the female body" could somehow prevent pregnancy from "a legitimate rape." Party leaders aren't responsible for every candidate's gaffe. And Republican primary voters, not party honchos, choose nominees. But it's easy to draw ideological lines from Palin to O'Donnell to Akin and so on to some of the far-from-mainstream presidential contenders of 2012 and today.

Then-Rep. Michele Bachmann (Minn.) was rising fast in Republican presidential polls in July 2011. Pizza company executive Herman Cain led the polls three months later. Does anyone now think Bachmann and Cain had the skills, experience and temperament to be president? True, the party eventually settled on Mitt Romney. But for months, Americans wondered, "Is this party serious?" Now the Republicans' leading presidential contenders are Trump - who vows to make Mexico pay for a "great, great wall" on the U.S. side of the border - and Ben Carson, who questions evolution and asks why victims of the latest mass shooting didn't "attack the gunman." This isn't to heap new scorn on Palin. But let's not diminish the recklessness of those who championed her vice presidential candidacy. It was well known that McCain, 72 at the time of his nomination, had undergone surgery for skin cancer. It wasn't preposterous to think Palin could become president.

Now Republicans ask Americans to give them full control of the government, adding the presidency to their House and Senate majorities. This comes as Trump and Carson consistently top the GOP polls. Republican leaders brought this on themselves. Trump calls Palin "a special person" he'd like in his Cabinet. That seems only fair, because he's thriving in the same cynical value system that puts opportunistic soundbites above seriousness, preparedness and intellectual heft.

William M. Daley was White House chief of staff from 2011 to 2012.