The Wisconsin presidential primary is emerging as a crucial lifeline for Republicans desperate to stop Donald Trump's march to their party's nomination.
One of his worst weeks of the 2016 campaign is colliding with a state already sceptical about his brash brand of politics.
A big loss for Mr Trump in Wisconsin on Tuesday would greatly reduce his chances of securing the delegates he needs to clinch the Republican nomination before next July's national convention.
It could also offer new hope to rival Ted Cruz and outside groups that see Mr Trump as a threat to the future of the Republican Party.
"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," Mr Cruz said.
Mr Trump's view is rosier for his own campaign: "If we win Wisconsin, it's pretty much over."
But almost nothing has gone right for him since Wisconsin stepped into the primary spotlight.
Even before he arrived, Mr Trump was skewered in interviews with a trio of Wisconsin's influential conservative talk radio hosts.
On Tuesday, just hours before his first campaign stop, two-term governor Scott Walker threw his support behind Mr Cruz, of Texas.
Much of the trouble that followed was of the Trump campaign's own making.
Corey Lewandowski, Mr Trump's campaign manager, was charged with assault for an altercation with a reporter.
Then Mr Trump was forced into a U-turn on his assertion that women should be punished for getting abortions, a comment that managed to unite both sides of the abortion debate in fierce opposition to his statement.
"As soon as he stepped foot in Wisconsin the mask finally came off," said Jim Steineke, the Republican majority leader in the Wisconsin Assembly.
"Part of it is just the Wisconsin nice. We don't take too kindly to people who act the way Donald Trump acts."
A week before the primary, a poll run by Marquette University Law School showed Mr Trump lagging behind Mr Cruz by about 10 points - a dramatic fall for the candidate who led in the same poll last month.
If Mr Cruz sweeps all the delegates in Wisconsin, Mr Trump will need to win 57% of the remaining delegates in other states to collect the 1,237 he needs to clinch the nomination. So far, he has won 48% of all delegates awarded.
Wisconsin offers 42, putting it in the middle of the pack of primary prizes. But the state's stature in Republican politics and its position on the calendar - no other state votes until April 19 - have elevated its importance.
Though the state has voted for Democrats in the past several presidential elections, it boasts prominent national party leaders including Mr Walker and House Speaker Paul Ryan.
Anti-Trump groups say they have benefited from the primary calendar, as rival campaigns have been able to focus narrowly on Wisconsin for nearly two weeks.
Planned Parenthood and Priorities USA, two groups working to elect Democrat Hillary Clinton, have teamed up for their first anti-Trump advertisement of the election year, a 30-second spot playing on websites that features his abortion comment.
"When it comes to women, the Republican frontrunner is demeaning, insulting and dangerous," the ad reads.
Mrs Clinton herself said: "Donald Trump is showing us exactly who he is and we should believe him. But let's remember this, all the Republican candidates want to make abortion illegal."
While Wisconsin may provide a much-needed boost for Trump opponents, the real estate mogul will soon find himself back in friendly territory.
The next contest awaiting Republicans comes on April 19 in New York, Mr Trump's home state and one of the biggest delegate prizes up for grabs.
Mrs Clinton, a former New York senator, holds a formidable lead among delegates but opponent Bernie Sanders hopes a series of recent victories in the West might turn into a springboard for a win in Wisconsin.