Republican U.S. presidential candidate Donald Trump delivers a speech at a campaign town hall event in Wausau, Wis., April 2, 2016.
Republican U.S. presidential candidate Donald Trump delivers a speech at a campaign town hall event in Wausau, Wis., April 2, 2016.

Billionaire real estate mogul Donald Trump is drawing new attention for his views on abortion, NATO, nuclear arms and his treatment of women as his political challengers try to cut into his lead as the front-running U.S. Republican Party presidential candidate.

Political analysts are suggesting his unexpected surge to the nomination has been slowed as Republicans and others begin to question his views and say that his chances are bleak of winning November's election against the expected Democratic Party nominee, former Secretary of State Hillary Clinton.

In recent days, major news outlets have reported he would be the candidate with the worst national favorability ratings to win a major party presidential nomination in three decades and political surveys show him losing badly in the national contest to replace President Barack Obama, who he leaves office next January.

US Presidential Candidate Delegate Count

Trump, who has never held elective office, has a significant lead in winning delegates to July's Republican national convention, where the party will pick its 2016 presidential nominee. But Trump could end up short of winning a majority of delegates before the start of the quadrennial gathering, throwing the contest to a contentious second ballot or perhaps more.

Wisconsin  polls

The one-time television reality show host faces voters Tuesday in Wisconsin, the next state to vote in the months-long Republican nomination contest.  Political surveys in the northern state show Trump's nearest challenger, Texas Senator Ted Cruz, ahead of him in the state contest for 42 national convention delegates.

Cruz said Saturday that Trump's nomination would be "a trainwreck" in a national election face-off against Clinton.

Trump, campaigning in Wisconsin, fought back against any contention that he is not capable of handling the demands of the presidency and noted that while he negotiated business deals across the globe for decades, he never had been asked about the numerous issues he is now is being confronted with.

"I have good common sense," he told one rally. "I have good business sense."

Hillary Clinton is seen at 2016 Black Girls Rock!
Hillary Clinton is seen at 2016 Black Girls Rock! at New Jersey Performing Arts Center, in Newark, N.J., April 1, 2016.

In recent days, Trump has taken several positions on abortion, still a divisive issue in U.S. politics 43 years after the U.S. Supreme Court ruled that women have a right to end their pregnancies if they choose to.

Trump drew attacks from both abortion supporters and those opposed to it last week when he told one interviewer that if the medical procedural were ever made illegal in the United States, there should be "some form of punishment" for women who end their pregnancy.

Within hours, he reversed himself and said doctors, not women, should face criminal charges for performing abortions, if they were prohibited.

US laws on abortion

Days later, he said U.S. abortion rights should stay the way they have been, unless he could, if he is elected, appoint Supreme Court justices who would overturn their 1973 approval.

In other comments, Trump said he would be okay if the North Atlantic Treaty Organization, the U.S.-European military alliance since the end of World War Two, broke up because he said some countries in Europe are not paying their fair share and are "ripping off the the United States."

"Either they have to pay up for past deficiencies or they have to get out," Trump said, "and if it breaks up NATO, it breaks up NATO."

Democratic presidential candidate Sen. Bernie Sand
Democratic presidential candidate Sen. Bernie Sanders of Vermont addresses the crowd at a campaign rally at the University of Wisconsin-Eau Claire, April 2, 2016.

Even as world leaders met in Washington on ways to curb nuclear arms development, Trump suggested that perhaps both South Korea and Japan should have a nuclear arms capability to thwart North Korea.

He said he would not rule out U.S. use of tactical nuclear weapons against Islamic State jihadists in the Middle East.

Falling in US polls

Political surveys show Trump's popularity among female voters has plummeted, to 70 percent or more unfavorable ratings, in the wake of his abortion comments and his defense of his campaign manager, who is accused of battery for grabbing a female reporter by the arm a month ago as she tried to ask Trump a question.

But Trump, who rarely acknowledges any mistakes, told a New York Times columnist that he erred in retweeting an unflattering photo of Cruz's wife, Heidi, side-by-side with a glamorous one of his wife, Melania, a one-time fashion model.

In the Democratic race, Clinton has a substantial lead in the delegate race for the party's nomination.

But polls in Wisconsin show her locked in a tight contest in the state with her lone challenger, Vermont Senator Bernie Sanders, who has focused his campaign against Wall Street and growing income inequality in the United States.

Republican presidential candidate Sen. Ted Cruz of
Republican presidential candidate Sen. Ted Cruz of Texas speaks to the media before watching the movie, "God's Not Dead 2," in Ashwaubenon, Wis., April 2, 2016.