Donald Trump on the defensive ahead of Wisconsin primary

As Donald Trump faces a rough patch in his campaign to secure the Republican presidential nomination, Tuesday's Wisconsin primary has emerged as a possible lifeline for his opponents within the party.

Aloss for Trump in Wisconsin would greatly reduce his chances of securing the delegates he needs to clinch the nomination before July's national convention. It could also offer new hope to rival Ted Cruz and outside groups that see Trump as a threat to the future of the Republican Party.

And it comes on the heels of one of the worst weeks of the business mogul's campaign, withina state already skeptical of his brash brand of politics.

• Tom Mulcair calls Donald Trump a 'fascist'

"I think the whole country is looking to Wisconsin right now to make a choice in this race, and I think the choice Wisconsin makes is going to have repercussions for a long time to come," Cruz said Thursday in an interview with Milwaukee radio stationWTMJ.

If Cruz sweeps all the delegates in Wisconsin, Trump will need to win 57 per cent of the remaining delegates in other states to collect the 1,237 he needs to clinch the nomination. So far, he has won 48 per cent of all delegates awarded.

Wisconsin offers 42 delegates,putting it in the middle of the pack of primary prizes. But the position of the state on the primary schedule falling two weeks after the previousRepublican primaryand two weeks before the next haselevated its importance.

• Trump says abortion ban should yield 'punishment' for women

Anti-Trump groups say they have benefited from the primary calendar. SuperPACsand rival campaigns have been able to focus narrowly on Wisconsin for nearly two weeks.Trump's rival candidates and outside groups opposing him are slated to spend a combined $3.8 million in advertising in the state.

• Trump defends campaign manager charged with battery
• ANALYSIS|Trump's war on political correctness redefining U.S. race

A bad week

Trump has been flying high throughout most of the campaign, winning key primaries andgaining in the polls despite numerousgaffes and controversial statements.

But almost nothing has gone right for him since Wisconsin stepped into the primary spotlight.

Even before he arrived, Trump was skewered in interviews with a trio of Wisconsin's influential conservative talk radio hosts. Last Tuesday, just hours before his first campaign stop, two-term Gov. Scott Walker threw his support behind Cruz, of Texas.

And much of the trouble was within Trump's own campaign.

His campaign manager, CoreyLewandowski, was charged with simple battery, accused of grabbingBreitbartNews reporter Michelle Fields's arm after a press conference, an encounter that was captured on surveillance footage.

Unflattering photo a 'mistake'

And Trump was already under fire for comments about rival Ted Cruz's wife, whichprompted new concerns about Trump's ability to appeal to female voters in the general election. He attempted to make amends on Saturday after a rally in the Milwaukee suburb of Racine.

Offstage, he expressed regret that he had retweeted an unflattering photo of Cruz's wife, Heidi, paired with a glamorous photo of his own wife, Melania, as part of a bitter feud between the two men.

"Yeah, it was a mistake," he told New York Times columnist Maureen Dowd. "If I had to do it again, I wouldn't have sent it."

One of his biggest missteps has been recent comments on abortion.

During a town-hall taping on Wednesday, Trump was asked whether abortions should be illegal and whether women should be punished for having them. His answer, "that there has to be some form of punishment," drew quick criticism and an unprecedented written reversal from the typically unapologetic candidate.

'Wisconsin nice'

"As soon as he stepped foot in Wisconsin the mask finally came off," Republicanstate Rep. Jim Steineketold the Associated Press."Part of it is just the Wisconsin nice. We don't take too kindly to people who act the way Donald Trump acts."

Republican voter Linda Ruddy, a 48-year-old dental hygienist from Oshkosh, agreed.

"He's rude. He's arrogant. He's a loose cannon. He's insulting to women," Ruddy said.

A poll run by Marquette University Law School has shown Trump holding steady at around 30 per cent in Wisconsin, a level of support that gave him a lead in the state last month.But the latest survey released this week showed Cruz surging past the real estate mogul, topping him by 10 points.

A contested convention?

To win the nomination, a candidate must secure 50 per cent, plus one, of the 2,472 partydelegates. Ifnobody gets a clear majority, July willsee the party head into its first contested national convention since1976.

• 6 things to know about the presidential primaries

In that case, all bets are off and anyone can win. Delegates are only beholden to theircaucus or primary's choice of candidate on the first round of voting. After that, they're free to support whomever they choose, in as many rounds of voting as it takes.

That's what some establishment Republicansarehoping for.

Mitt Romney has encouraged voters to force a contested convention to keep Trump from winning. Marco Rubio's campaign team has indicated it would be his best shot at securing the nomination. And, according to theWashingtonPost, partyelites are already working on strategies to use a contested convention against Trump.

Current party rulesrequiringthe nominee to have won a majority of delegates in at least eight statesfavour Trump and Cruz.But the rules can easily be changed by a committee at the convention.

That means final victory can go to anyone atrailing candidate, a candidate who dropped out or even someone who never ran at all.

Still, Trump's team has maintained he can win Wisconsin. And even if he fails to secure the nomination,he could still be in the running for president.

In an interview Friday, to be broadcast on Fox News Sunday,Trump was asked whether he'll considerrunning as an independent if he loses the Republican race.

He replied: "I'm going to have to see how I was treated."