Washington, Aug 21 Hillary Clinton and Donald Trump emerged clear winners in Democratic and Republican primaries in key swing states of Florida, Ohio and Pennsylvania, but how they do in the presidential election is another story, according to a new poll.

Surprisingly, Vice President Joseph Biden runs as well as, or better, than the former secretary of state against top Republicans in general election matchups in these key swing states, according to a Quinnipiac University Swing State Poll released on Thursday.

While they lead in the race for the nomination, Clinton and the real estate mogul Trump have the worst overall favourability ratings among all voters of any of the leading candidates, and the lowest scores for being honest and trustworthy.

The Swing State Poll focused on Florida, Ohio and Pennsylvania because since 1960 no candidate has won the presidential race without taking at least two of these three states.

Former Florida Governor Jeb Bush and Republican Senator Marco Rubio both run better than Trump against Clinton, Biden or Democratic Senator Bernie Sanders of Vermont.

\"Hillary Clinton\'s poll numbers are like a leaky faucet: drip...drip...drip,\" said Peter A. Brown, assistant director of the Quinnipiac University Poll.

\"She is now getting less than half the vote in all three states\' Democratic primaries.\"

\"Perhaps most telling is how poorly she scores when all voters in these three key states are asked about her empathy, honesty and temperament,\" he added.

In Florida, Ohio and Pennsylvania, she averages a negative 37-55 percent favourability. Donald Trump is in the same leaky boat, averaging a negative 34-53 percent favourability.

The good news for Clinton however is that she remains far ahead of Senator Bernie Sanders and Biden in the three Democratic primary contests.

But the poll brought better news for \"Biden, who is spending his time in seclusion, contemplating whether to take on Clinton.

\"In head-to-head matchups against the three leading contenders for the Republican nomination, he runs as well, or slightly better than, she does,\" Brown said.

\"The first Republican debate mattered,\" he said. \"Jeb Bush got middling debate grades and slips in the Republican horse race.\"

\"Yet, he does very well when voters rate the leading Republican candidates on personal characteristics.

\"He scores best on honesty, empathy and temperament to handle an international crisis, while finishing a close second to Trump on leadership,\" Brown said.

\"Wisconsin Gov. Scott Walker gets very low debate grades and all but disappears from the Republican primary list.\"

Hillary Clinton\\\'s poll numbers falling, drip by drip