Now that the Republican race is effectively over, will Haley's supporters go to Trump?

The evidence is now irrefutable for what's seemed obvious for weeks: Donald Trump will be the Republican nominee this fall in a presidential rematch against Joe Biden.

A string of Super Tuesday victories made clear Trump will mathematically clinch his party's nomination this month, in record time for a non-incumbent.

He captured all but one of the 15 states voting Tuesday and has now amassed more than nine-10ths of the delegates who will anoint the nominee.

Here's what's not yet obvious: Will holdout Republicans get past their aversion to him and rally to his side for the November election?

It's a question that could well decide the U.S. presidential election.

For weeks, Nikki Haley voters have been grappling with this dilemma, as it became increasingly obvious this moment was coming.

On Tuesday, when asked that question, Claudia Barbish raised her eyes as she contemplated the unwelcome scenario of voting for Trump.

"Ah, that's a tough question," said Barbish, a Republican, outside a polling station Tuesday in Fairfax, Va., where she cast a ballot for Haley.

"Probably," she went on. "I think I would respect [Trump] as a leader. From a personal standpoint, he's not my favourite."

Trump needs others to follow her example.
 

In close election, Haley voters matter

Longtime party strategist Karl Rove pulled out a whiteboard on Fox News, late Tuesday, illustrating a potential impediment to Trump's comeback.

He listed the conspicuous clusters still voting against Trump in Republican primaries: more than 20 per cent in numerous states, more than 30 per cent in a few, and half the voters in Vermont. Many of those primary voters are not actual Republicans, but Democrats, who participated to vote against Trump in states that allow cross-party primary voting.

But actual longtime Republicans are wrestling with this decision.
 

Republicans grappling with what to do next

Decades-long friends debated that question on a sidewalk after a Haley rally, late last month in Georgetown, S.C.

Becky Ward Curtis said she's "sick" of Trump. In her 77 years, she said, she can't recall anyone bringing more vitriol into U.S. politics.

Will she vote for him, though? 

"Most definitely," said the longtime Republican. "I would definitely vote for him [Trump]. I would never vote for Biden. I'm not an idiot." 

Her friend disagreed. 

Barbara Mathis, a semi-retired nurse, said she voted twice for Trump. There won't be a third time, she promised. She said she was irrevocably turned off by his behaviour in his post-presidency.

"I would write her [Haley] in," Mathis said. "Because his moral compass is wrong."

Trump predicts there will be enough voters like Barbish and Ward Curtis. He expressed confidence the party would come together, in a victory speech at his Florida mansion on Tuesday night. Haley did not speak publicly. 
 

"We're going to have unity. And it's going to happen very quickly," Trump said. 

That is also consistent with most recent surveys. Most polls show Trump uniting his party, and leading Biden.

Biden's defenders insist those surveys mean little: In byelections, and in primaries, they say real election results show Republicans and Trump under-performing versus the surveys.

That pattern appeared to have snapped Tuesday as the former president hauled in big wins in most states, on a scale comparable to the surveys. 

So are these general-election polls to be believed?

WATCH | Trump inches closer to Republican nomination: 

The outlook, entering the general election

An analyst of public opinion data says it's fair to take a skeptical view of surveys — within limits. He also sees real flashing signals for Biden.

"It's a little bit too far when some Biden surrogates say, 'Well, you know, polling is broken. We're not worried at all,'" said Marc Trussler, director of the Program on Opinion Research and Election Studies at the University of Pennsylvania.

"I think there's certainly reasons to be concerned if you're Biden.'" 

For example, he said, it's a bad sign for Biden that he still gets poor marks for handling the economy, even with the economy improving.

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So the U.S. may be enjoying the best economic growth, by far, among all countries in the Organization for Economic Co-operation and Development (OECD), and historically low unemployment, and record-high stock prices.

Biden may have notched major legislative wins on drug prices, infrastructure and clean tech. Trump may be facing 91 criminal charges, running on authoritarian-sounding promises to punish his political enemies.

Yet Americans are angry. About lingering inflation. About a porous border. And about foreign wars, including the one in Gaza that has created a backlash within Biden's party.

That discontent is evident in an ongoing protest vote. 
 

While Biden is easily cruising to his own nomination, more than 10 per cent of voters in Democratic primaries have now opted for none-of-the-above in several states. 

Now Americans will be asked to choose between two unusual candidates: an unpopular 78-year-old under indictment, and an unpopular 81-year-old they see as frail.

The winner of this improbable battle will be the candidate who most unites his party.

A Democratic strategist, Van Jones, speaking on CNN, delivered a clarion call to his allies, warning this won't be easy: "Get ready for the fight of your life."