Donald Trump swaggered back on to New York’s campaign trail poised for a win in Tuesday’s crucial primary election, armed with an unusual new strategy for a self-declared winner: portraying himself as the victim of a Republican elite plotting to deny the popular will.

The businessman has dominated polls in his home state and is likely to use victory there as proof that he is leading a grassroots movement, one that could make for a bitterly contested and even explosive summer convention.

“You’re going to have a very, very angry and upset group of people at the convention,” Trump said at an event in Staten Island, New York, on Sunday. “I hope it doesn’t involve violence, and I’m not suggesting that. I hope it doesn’t involve violence and I don’t think it will. But I will say this: it’s a rigged system, it’s a crooked system, it’s 100% crooked.”

Reince Preibus, the chairman of the Republican national committee (RNC), was forced to offer assurances on CBS’s Face the Nation on Sunday: “We’re going to have plenty of security, plenty of protection for the delegates.”

Trump has previously warned that there could be “riots” if he is denied the nomination despite winning the most votes during the primary season. Trump leads Texas senator Ted Cruz by 744 to 559 delegates, but the combined total of non-Trump delegates is 890. A candidate needs 1,237 delegates to clinch the nomination outright. On the first ballot most delegates are bound to vote according to their state’s results; on subsequent ballots they become free to choose.

$1,000-a-plate Republican gala highlights clash of 'New York values' Read more

The former reality TV star needs an emphatic win in New York after a string of setbacks, including on Saturday in Wyoming, where Cruz swept all 14 delegates at stake at the party convention. If Trump wins most of New York’s 95 delegates, he will probably claim vindication and further condemn the complicated, state-by-state rules that govern how Republicans choose their nominee. He previewed the assault on Friday with an op-ed in the Wall Street Journal.

Trump, once a fixture on Sunday political talkshows, skipped them for the second week running as part of his campaign’s quieted tenor.

On Fox, his campaign manager, Corey Lewandowski, was asked what the frontrunner meant by warning on Saturday that the RNC faces a “rough July” at a contested convention. Lewandowski said: “Anything that they’re going to potentially try and do to stop him from being [the nominee] is going to be detrimental.

“What we’re talking about is a fractured party,” he added. “What we’re talking about is millions of people who’ve turned out to support Donald Trump, and now they’re saying potentially they’re going to try and take this away from Donald Trump at a convention. That’s not what we’re about. We’re supposed to be bringing the party together.”

The candidate now stands poised to declare himself the darling of disenfranchised conservatives, if not Republicans at large. A CBS News poll shows him with 54% support among Republican New York primary voters, with Cruz on 21% and John Kasich on 19%. On Wall Street, one worker reflected on Cruz’s derisive references to “New York values” by telling the Washington Post: “Life, liberty, the pursuit of happiness – and Ted Cruz is a complete A-hole. That’s a New York value.”

With other upcoming states also looking favourable to Trump, his campaign’s protests that party leaders are conspiring to snatch the nomination away at the expense of ordinary people are likely to reach new extremes. He has received about 8.2m votes to date, about 2m more than Cruz. “He is the presumptive nominee going forward, and Ted Cruz is going to be mathematically eliminated from gaining 1,237 delegates by next Tuesday,” Lewandowski said.

The Trump campaign could also point to a national NBC News/Wall Street Journal poll, released on Sunday, showing that nearly two in three Republican voters agree with his argument about the convention. The respondents said the candidate with the most votes should be the party’s nominee if no candidate wins a majority before the convention.

The rise of Donald Trump is a battle for the soul of the Republican party Read more

But Kasich, whose slim hopes rest entirely on a contested convention, compared Trump to a petulant schoolboy. “You’ve got to have a certain number of delegates to be nominated, and, you know, it’s like saying I made an 83 on my math test so I should get an A just because I think it’s rigged that you have to get a 90 to get an A,” he told CNN. “I mean, come on. Act like you’re a professional, be a pro.”

And as he toured the studios on Sunday, Priebus dismissed Trump’s apparent threat of convention chaos as “rhetoric and hyperbole”.

He acknowledged, however, that he had contacted the rules committee before a meeting next week to discourage amending the process. “In a politically charged environment,” he told CNN, “I think it’s too complicated.”

Any recommendations that party leaders might have are “not a good idea”, he said, because they cannot actually change anything.

“It’s up to the delegates at the convention. So the recommendations, I think, just confuse people. I think it’s a bad idea.”