Washington - The vast majority of Americans say they are afraid of at least one of the two major candidates - Hillary Clinton or Donald Trump - winning the White House, a remarkable finding that reflects an unsettled nation unhappy with its choice.Nearly 81% of Americans say they would feel afraid following the election of one of the two polarising politicians, according to a new AP poll. That includes a quarter who say it doesn't matter who wins: they're scared of both.Political conventionsThree-quarters of voters say their pick for president is motivated by a desire to cast their Election Day ballot against Clinton or Trump, more than those who say they're voting for the candidate who shares their positions on the issues or is the most qualified to hold the office.On the eve of the summer's political conventions, at which the general election campaign officially begins, the latest poll findings underscore the deep sense of unease that is sharpening the political divide in America and shaping an already nasty race for president.So much so that notable numbers of Americans even hold negative views about the candidate they want to win: 14% of both Trump's and Clinton's supporters say they're backing a candidate they don't like.The survey was conducted after the fatal police shootings of two black men by police officers last week in Louisiana and Minnesota and mostly after a sniper seeking revenge for those slayings killed five police officers in Dallas during a peaceful protest march.Would be proudThe poll found Americans hold resoundingly negative opinions of both candidates. About 57% have an unfavorable view of Clinton, compared to 37% who have a favourable view. About 63% have a negative view of Trump, compared to the 31% who think well of him.Fifty-six percent of Americans said they would feel afraid and 48% say they'd feel regret if Trump wins the White House. Just 22% said they'd be proud and 26% excited should America pick Trump on Election Day.Clinton doesn't fare much better: If she's elected president, 48% say they would be afraid and 46% say they would feel regretful. Only 27% of Americans would be proud of that choice and 26% would be excited at her election.