WASHINGTON (CNN) — Everyone said it wouldn't happen. Everyone was wrong.

Donald Trump pulled off one of the most unlikely electoral coups of modern times this week, toppling the political and media establishment to become the presumptive Republican presidential nominee. His domination of the primary season, which effectively ended Wednesday when Ohio Gov. John Kasich dropped the last remaining challenge to Trump, was unthinkable just weeks ago when the political conversation still centered on the potential of a contested convention.

But a campaign initially dismissed as a joke — The Washington Post's Dana Milbank promised Thursday to honor his vow to eat his column in penance — confounded the pundits to such a degree that all bets are off about how the rest of the 2016 campaign might unfold. Even Trump himself seemed surprised by the swiftness at which he locked down the nomination. In an interview with CNN's Wolf Blitzer Wednesday, Trump said he expected Democratic front-runner Hillary Clinton to finish her primary campaign before him.

'Thought I'd be going longer'

"I'm even surprised," Trump said. "I thought I'd be going longer, she'd be going shorter."

But the grind of presidential politics leaves no time for savoring victory.

In his first full day as the presumptive nominee, Trump's campaign had to quickly shift gears from a primary fight to a search for a running mate. Meanwhile, Trump faces a host of new questions about his prospects against Clinton in the fall, including whether his unorthodox approach to winning the GOP primary will translate into a general election battle against one of the biggest names in politics.

"It is a big challenge but he has already defied every single thing of political gravity that we have known," said Mike Shields, former Chief of Staff for the Republican National Committee.

"Who's to say that he can't do all of these things and then some," Shields said on CNN's "New Day."

Trump is starting from a tough place.

A new CNN/ORC poll on Wednesday found that Clinton leads Trump 54 percent to 41 percent in a potential general election match-up — her biggest lead since July. She is more trusted than him on issues ranging from foreign policy to education and health care.

Still, by a 50 percent to 45 percent margin, voters say Trump would do a better job handling the economy than Clinton. And almost 9 out of 10 voters in the poll called the economy extremely or very important to their vote, outranking any other issue tested in the poll.

The political skills that Trump brought to the primary fight could prove potent in a race already shaping up as a bitter, nasty personal clash with Clinton.

After all, the tough tactics from the political neophyte disrupted one of the most experienced Republican fields in a generation. He destroyed the political hopes of Jeb Bush with his "low energy" jibe. Trump's brawling tongue also obliterated — at least for now — the potential of the GOP's next generation of political rock stars, "Lyin" Ted Cruz and "Little" Marco Rubio.

He's trying to take a similar approach to Clinton, dubbing her "Crooked Hillary."

Revolutionizing campaigns

With an unerring eye for a rival's weaknesses, he revolutionized how campaigns are won, becoming a master of social media, hijacking news agendas with skills honed on a reality television and a mastery of targeted marketing.

And with undeniable political skill, Trump — a multi-billionaire with a Boeing equipped with gold seat belts — became an earthy cypher for ignored blue collar Americans who revile conventional politicians as they struggle to get by in a wounded economy.

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Trump's open path to nomination causes agony for some in GOP

Donald Trump's last Republican foe, Ohio Gov. John Kasich, ended his quixotic presidential campaign Wednesday, cementing Trump's remarkable triumph as his party's presumptive nominee and launching him toward a likely fall battle with Hillary Clinton. Some Republican leaders began reluctantly rallying around Trump, but others agonized over their party's future.

Using just a few issues, like illegal immigration, the toll wreaked on industrial communities by free trade and by playing into a wider sense of national decline with his "Make America Great Again" message, Trump made himself an unstoppable political force. His bite was so intimidating that by the time competitors such as Bush, Cruz and Rubio mustered the courage to lambast his past, his character and his politics, their campaigns were already faltering.

Clinton may not make a similar mistake. In an interview Wednesday with CNN's Anderson Cooper, she showed no problem hitting Trump.

"He's a loose cannon," she said. "And loose cannons tend to misfire."

And deeper questions also lurk around Trump. They begin with: What will the rest of America think?

Even though, in recent primaries, Trump lifted his vote totals easily above the 50 percent mark, his core support in the blue collar Republican electorate still represents a minority of opinion in a nation that is becoming more diverse and less white.

That's fueling questions about whether Trump has already inflicted fatal damage on the Republican Party's hopes of winning back the presidency after eight years. After its defeat to President Barack Obama in 2012, the GOP determined it needed to do more to reach out to women, minorities and socially moderate voters, or risk being washed up by the tides of demographic change sweeping the country.

Rock-bottom approval ratings

Yet Trump enters the general election with rock-bottom approval ratings among Hispanics, African-Americans and women voters — and appears to need a mythically large turnout from white American males if he is to prevail in November.

His rudimentary policy platforms will come under increasing scrutiny, like the apparently unspecified plan he says will destroy ISIS within months.

It's the same story for his fiscally questionable promises to simultaneously cut taxes, raise military spending, take care of veterans, safeguard social safety net programs and eliminate the national debt.

Then voters will have to decide if they are willing to elect a President whose impact is already reaching far beyond the nation's borders, triggering palpable concern abroad at the prospect of 70 years of the post-World War II international order being torn up by a foreign policy neophyte brandishing an "America First" slogan.

Trump will be the first major party nominee not to have served in major elected office since Dwight Eisenhower. Though given Eisenhower's status as a national hero for masterminding the military defeat of Nazi Germany, a more apt comparison to Trump might be the New York businessman Wendell Willkie, a former Democrat who was nominated by the GOP in 1940.

Trump's critics worry that his political rhetoric on issues from immigration to women's rights take American politics closer to the dark fringes of demagoguery than it has been for decades.

The Democratic barrage — playing into such fears — has already begun.

Massachusetts Sen. Elizabeth Warren went on the attack soon after Trump's triumph in Indiana on Tuesday, tweeting that Trump built his campaign on "racism, sexism, and xenophobia" and that what happens next "will determine whether we move forward as one nation or splinter at the hands of one man's narcissism and divisiveness."

But Trump may not be the only victim of a negative campaign.

A no-holds-barred race in which both presidential nominees rake over the other's substantial political baggage could leave the eventual winner irrevocably damaged and facing a disabled presidency from the start.

Many Democrats believe that Trump's victory in the GOP primary means they are almost certain to keep the White House. However, as the past year has proven, they would be unwise to underestimate the power of Trump.

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