Republican front-runner Donald Trump has said he would easily win the Republican nomination if John Kasich drops out of the contest.
He said the Ohio governor should not stay in the contest because he cannot collect enough delegates to win.
His comments came just ahead of Tuesday's Wisconsin vote which could reshape the Republican race.
"If I didn't have Kasich, I automatically win," Mr Trump said at a rally in Wisconsin.
If Mr Trump loses the primary contest on Tuesday, as the polls suggest, it is far less likely he will have the all-important 1,237 delegates needed to secure the nomination.
Delegates represent their states at the party's convention and are accumulated by the votes in each state.
Currently, Mr Trump has 735 delegates, Texas Senator Ted Cruz 461 and Ohio Governor Mr Kasich 143.
If no-one hits 1,237 after all 50 states have voted, the Republican convention in July is contested, meaning the delegates vote for a nominee, and Mr Trump, who is unpopular among sections of the party, could lose the nomination.
The New York businessman has had a very difficult seven days, sparking outcry over comments he made about abortion, standing by his campaign manager after he was charged with assaulting a reporter and raising eyebrows with remarks about US foreign policy.
"Was this my best week? I guess not," Mr Trump told "Fox News Sunday".