After a primary season that broke the rules and confounded the experts, Republicans and Democrats are now grappling with the same questions: What kind of candidate would Donald Trump be in a general election and how should Hillary Clinton run against him?
At Trump headquarters, officials were beginning to think seriously about the shape of the general campaign before the candidate's win in Indiana and Senator Ted Cruz's withdrawal from the race.
Trump still needs about 200 delegates to formally secure the nomination, but Cruz's decision to end his campaign removed his last major obstacle. Trump won at least 51 of 57 possible delegates, pushing him to 1047 of the 1237 needed to clinch the nomination, compared with 153 for Governor John Kasich. Cruz had 565 delegates.
"Ted Cruz - I don't know if he likes me or he doesn't like me - but he is one hell of a competitor," Trump said.
The areas the Trump campaign is considering include the core issues of his message, the look and feel of the Republican convention, electoral map strategies and what, if any, changes the New York billionaire might need to make - stylistically or otherwise - to expand his appeal.
Officials say two things are not likely to change.
First, Trump will continue to be an outspoken candidate prepared to say unpopular or imprudent things. "What has been a certainty in this race is that Mr Trump is going to be Mr Trump," said campaign manager Corey Lewandowski. "That is to say, his appeal has been as a person who tells it like it is."
Second, officials say, Trump's lack of predictability - what critics regard as his lack of discipline - will prove to be an asset against Clinton, whom they regard as a far more conventional candidate. "Mr Trump is a candidate who has the ability to change the narrative at any moment," Lewandowski said. "Any other candidate would run a traditional campaign against Hillary Clinton."
Clinton's team and those at outside groups allied with her campaign are making similar assessments, looking for their own opportunities to expand the map into some traditional Republican states while going to school on mistakes made by Trump's rivals during the primaries. One big lesson is that Trump's opponents waited too long to go after him and were timid when they did. Clinton and the Democrats probably will go early and hard against him.
Clinton allies see Trump as a deeply flawed candidate - he has higher negative ratings than any past nominee in either party since polling began - with limited options to remake himself. They also doubt that he wants to change his style. As a result, Clinton's team is preparing for what could be one of the nastiest campaigns in recent memory.
"Hillary set out a year ago to be a champion for everyday people and to help families finally start getting ahead again in this economy," said Robby Mook, Clinton's campaign manager. "That's what she's going to keep talking about in the general election. ... Trump, I'm sure, will try to bully and throw out insults. That's not going to derail her." If some Republicans were hoping to see a more careful and judicious Trump, they had to be disappointed last week when he attacked Clinton for playing "the woman's card" and claiming that, if she were a man, "I don't believe she'd get 5 per cent of the vote".
To many strategists, that comment seemed like a classic mistake that took away from an otherwise celebratory event after sweeping five states. Instead, it could represent a template for the kind of campaign Trump runs, one that is slashing, politically incorrect, ideologically inconsistent and designed to try to keep his opponent off balance. He could try to come at Clinton from both the right and the left.
Some surveys and electoral map analyses suggest t Trump would be an almost certain loser against Clinton and that his defeat would be sizeable enough to take many other Republicans down with him. Other recent polls show the former Secretary of State with only a narrow lead, which gives Republicans hope that once the two nominating conventions are over, fears of a Clinton presidency will drive many in their party to support Trump. Still, even Republicans who see strengths in Trump's candidacy and admire the campaign he is waging for the nomination look to November with great uncertainty.
"He has the biggest upside and the biggest downside of any candidate I've ever seen," said former House Speaker Newt Gingrich.
"If everything comes together and clicks, he'll be a historic figure. And if everything goes sour, we'll think of Goldwater and McGovern as medium-level disasters."
Some leading Republicans say privately that unless Trump makes changes in his approach ahead of the general election, the party is destined to be outside the White House for another four or eight years.
Trump's advisers are hoping to develop better lines of communication - and relationships - with national and state party officials in preparation for the convention and the general election.
Contrary to claims of Democrats, Paul Manafort, who was brought in recently as Trump's convention manager, says he anticipates that Trump's image will improve with time.
Trump's rhetoric has sent those negative ratings skyrocketing, whether his attacks on Mexican immigrants, his call for a temporary ban on Muslims coming into the country or his call - later retracted - for penalties for women who have abortions.
His advisers see his rhetoric differently. They argue that, while he has said provocative things that have drawn condemnation or criticism, including that the United States should rethink its position in Nato, over time some of his ideas have come to be seen as more acceptable or open to fair debate.
"He will not bow to being politically correct," Manafort said. "His instincts of what the American people are thinking have been accurate."
Mook said: "I think they can try to remake or remodel him in any way his consultants might choose. But we have to take him at his word that he's going to do everything he said he would do."
Attacks, rather than those issue contrasts, are likely to animate the general campaign, and here there's no sign that Trump is ready to alter his approach. If anything, he appears eager to take on Clinton.
Gingrich said that on the basis of his reading of Trump's record, the New York businessman has principles of action in which he truly believes. "These are not habits or personality quirks," he said. "He always counterattacks ferociously. He also finds a way to define his opponent in a way that shrinks and limits them. These aren't just barroom brawl tactics. They are to define semantically his opponents in ways they can't get out of, Hillary being the next great experiment."
Dan Pfeiffer, former senior adviser to President Barack Obama, says Trump presents a potentially unconventional target as a candidate. "He confounded a lot of very good strategists on the Republican side and he has the potential to do this here."
That, however, doesn't change Pfeiffer's broader analysis that Trump in the end cannot win the general election or that Clinton won't be prepared to parry the attacks. "She has a lot of experience dealing with misogynistic males."