The U.S. presidential election may turn out to be one of the world's biggest unpopularity contests.

Nearly half of American voters who support either Democrat Hillary Clinton or Republican Donald Trump for the White House said they will mainly be trying to block the other side from winning, according to a Reuters/Ipsos poll released Thursday.

The results reflect a deepening ideological divide in the United States, where people are becoming increasingly fearful of the opposing party, a feeling worsened by the likely match-up between the New York real estate tycoon and the former first lady, said Larry Sabato, director of the University of Virginia's Center for Politics.