Less than 36 hours away from a crucial primary test in Wisconsin, Donald Trump sounded Sunday night like a man who hasn't had the worst week of the political year.

As new Reuters polling results put his national numbers more than 13 percentage points above Sen. Ted Cruz's among Republican voters, the billionaire front-runner lashed out at Cruz, Ohio Gov. John Kasich, Hillary Clinton and President Barack Obama with the same cocksure fire that rally audiences saw for months before he hit last week's rough patch.

'Wisconsin – it's going to be such a big surprise on Tuesday!' he said, all but predicting a victory in a state where he trails Cruz in the polls.

'I'm down to two [opponents] and I'm beating the two by a lot,' he said, reflecting the Reuters poll, which found 44.6 per cent of GOP voters prefer him, compared with 31 per cent for Cruz and 17.8 per cent for Kasich.

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'HE'S A DIRTY ROTTEN CHEATER': Donald Trump laid into Ted Cruz on Sunday night in southeastern Wisconsin as Tuesday's statewide presidential primary loomed large

LEADING BADGER (FOR NOW): Cruz outpolls Trump by six to 10 points in Wisconsin but Trump promised a 'surprise' on primary day

'But Wisconsin is really important,' he conceded, knowing that it will either stall his momentum or leapfrog him a big step closer to the promised land.

Cruz, though, stands like a stone pillar in his way. And he came to Nathan Hale High School near Milwaukee on Sunday night to play the role of rhetorical bulldozer.

'I'm going to save your Social Security! Cruz wants to cut it in half!' he blared in the school's gymnasium, driving the point home with an almost taunting: 'You. Watch.'

Claiming Cruz is ill-equipped to tackle America's job losses and what he sees as weak trade policy, Trump boomed over growing applause that 'he's a disaster! And he's selling you people down the tubes!'

'And then he's doing phony commercials like he's for the working man. I just saw them. I said, "It's a disgrace." And I'm going to reveal it! It's a disgrace.'

He also reminded voters of the efforts of a few Cruz aides to sideline Dr. Ben Carson during the Iowa caucuses by spreading word – falsely – on the day of the vote that the surgeon had left the race.

'Frankly, if we had leadership in the Republican Party, they would have disqualified him for what he did in the state of Iowa. ... He's a cheater! He's a cheater! He's a dirty, rotten cheater!' Trump cried out.

But perhaps the most vicious anti-Cruz broadside of the night came from Trump's warm-up act, Stephen Miller, a top policy adviser who worked for Alabama Sen. Jeff Sessions before jumping aboard the Trump train.

Miller hammered Cruz for blaming the Trump camp for generating a National Enquirer cover story last month that speculated about five extramarital affairs the senator was alleged to have had.

PRODIGAL SON RETURNS: Corey Lewandowski, Trump's embattled campaign manager, made an appearance Sunday night – his first in recent memory. A female journalist has accused Lewandowski of battery stemming from an incident as she aggressively tried to ask Trump a question following a March press conference

U.S. Republican presidential candidate Donald Trump arrives at a campaign rally in West Allis, Wisconsin, today

MAKING THE PGA GREAT AGAIN? Jim Herman, a former Trump golf course pro whose career the billionaire bankrolled, won the Houston Open tournament on Sunday, qualifying for next week's Masters tournament

Cruz has denied the substance of that story but has refused to state that he has never been unfaithful to his wife Heidi.

Scoffing at the idea of a Trump hand in the story, Miller trumpeted: 'He'll probably bring up the DC madam story and claim we planted that too.'

That was a trial balloon designed to gin up more traffic for a Twitter rumor that has Cruz-linked phone numbers appearing in the 'little black book' once belonging to the late Deborah Jeane Palfrey, who ran an escort service for the rich and powerful.

Palfrey's lawyer hinted last week that he has records that might impact the 2016 election, and said he would consider defying a court order to release them.

Trump's Wisconsin hopes look bleaker than they did just weeks ago, as conservatives from the grassroots '#NeverTrump' movement – those who insist they will stay home rather than vote for him if he's the GOP nominee – rally around Cruz.

But he leads solidly among independent voters in the Badger State, and his lead over Cruz among potential Democratic 'crossover' voters is undeniable but hard to quantify.

That leaves the door open a crack for a surprise Trump victory in Tuesday's primary election.

Republican presidential candidate, Sen. Ted Cruz, R-Texas, waves to supporters as he arrives at a campaign stop at the Florian Gardens, Sunday, April 3, 2016, in Eau Claire, Wisconsin

Trump has lost primaries and caucuses to Cruz before, but always on days when he has won in other, larger states, giving him bragging rights and blunting the PR damage of a juggernaut that misses a step.

Coming after what may have been Trump's worst week yet on the campaign trail, Wisconsin's primary is seen as a proving ground for anti-Trump forces both inside and outside of the GOP.

The always-teflon Don has suddenly hit the skids – what some Wisconsin pols call 'the great wall of cheese,' as the swarm of controversies he has stoked for months seemed to catch up with him.

In a span of just a few days, the real estate tycoon was tempest-tossed by taking five separate positions on abortion, by suggesting America's Pacific-rim allies should arm themselves with nuclear weapons, and by defending– loudly – his embattled campaign manager against a battery charge filed by a journalist.

That campaign manager, Corey Lewandowski, showed up Sunday night and made a brief appearance near where reporters and photographers were working at the back of the gym.

But the usually gregarious New Hampshirite kept to himself and didn't answer journalists' questions.

'Was this my best week? I guess not,' Trump said during an interview with anchor Chris Wallace on 'Fox News Sunday.'

WHAT'S A TRUMP RALLY WITHOUT PROTESTERS? – One man disrupted Trump's speech for 10 seconds, shouting that 'The people of West Allis reject you!'

QUIET(ER) RIOT: Other anti-Trump activists were escorted out after staging a silent protest Sunday night

Cruz partisans hope a decisive win will slow the billionaire's momentum going into New York and other northeastern states where the Texas senator's following is far smaller.

New York's delegates awarded on April 19, together with the April 26 states of Connecticut, Delaware, Maryland, Pennsylvania and Rhode Island, total more than six times Wisconsin's.

Polls indicate voters there will hand more victories to the front-runner.

Trump also took a victory lap of sorts on Sunday, claiming credit for the launching the career of Jim Herman, a pro golfer who finished an improbable tournament run hours earlier in Houston with a victory at the Shell Houston Open.

'He's my golf pro, if you can believe it! .... Great guy, had no money but he had a lot of talent,' Trump said.

he recalled playing a round of golf with Herman when the newly minted champ was in his late twenties, and spotting a superstar.

'I gave him backing. I didn't have him write out a document. I just said "Here's some money, go on tour".'

'He'd be right now a teaching pro, giving people lessons on hitting the ball 12 yards' without his help, Trump said. 'Because he won today, he's in the Masters next week ... It's called talent, and that's what we need.'

CROWD CONTROL: Trump spoke to a few thousand ahead of a trio of Wisconsin events on Monday

Trump still faces an uphill climb to reach the magic number of 1,237 delegates, the smallest majority that will clinch the Republican presidential nomination during July's convention in Cleveland, Ohio.

The Republican front-runner predicted 'great success' Sunday morning despite polls of Republican and GOP-leaning Wisconsin voters that say he's trailing Cruz by anywhere from six to 10 percentage points.

'It feels to me like New Hampshire,' he told reporters after a breakfast drop-in at a diner in Milwaukee.

'A lot of people thought I was going to lose New Hampshire. And we won in a landslide.'

Trump led polls in New Hampshire for months before the voting, however.

'I think this has the feel of a victory,' he insisted, pointing to crowds who gathered to see him during three events on Saturday.

There are three more planned for Monday – including an evening rally with his wife Melania – before Trump is expected to return home to New York some time on election day.