U.S. Presidential Candidates Hillary Clinton, left, and Donald Trump
U.S. Presidential Candidates Hillary Clinton, left, and Donald Trump

WASHINGTON - Two new U.S. political surveys Sunday showed Democrat Hillary Clinton with a growing advantage in the U.S. presidential contest over her Republican challenger, Donald Trump, but they differed in the extent of her lead.

A Washington Post-ABC News poll said support for Trump, the billionaire real estate mogul making his first try for elected office, has plunged in recent weeks, giving Clinton a 51-to-39 percent edge nationwide among registered voters. Just a month ago, a poll by the same news organizations had Trump ahead of the former U.S. secretary of state, 46-44.

Another poll, by The Wall Street Journal and NBC News, showed Clinton, seeking to become the first female U.S. president, with a 46-41 edge, a two-point gain over the last month.

Democratic presidential candidate Hillary Clinton
Democratic presidential candidate Hillary Clinton gestures as she speaks during a rally in Raleigh, N.C., June 22,

An average of several recent polls give Clinton an edge of more than 6 percentage points after the race was believed to be virtually a deadheat a month ago.

The two newest polls come after a series of high-profile controversies involving Trump, including his attack on the Mexican heritage of an American-born judge hearing a consumer fraud case involving one of Trump's defunct businesses, Trump's firing of his campaign manager and weak campaign fundraising in May that was dwarfed by Clinton's.

Republican presidential candidate Donald Trump spe
Republican presidential candidate Donald Trump speaks during a news conference, at his Turnberry golf course, in Turnberry, Scotland, Britain, June 24, 2016.

Voter antipathy

The Post said its poll showed that about two-thirds of Americans think Trump is unqualified to be president, while about half are apprehensive about the prospects of a Clinton presidency, unheard of unfavorability ratings in a U.S. presidential race.

But both of them are expected to be officially nominated for president next month at their respective national party conventions. They then would face each other in the November 8 election to replace President Barack Obama when he leaves office next January.

The voter antipathy toward both candidates could give two other third and fourth party presidential contenders a role in determining the outcome of the quadrennial election.

The Wall Street Journal-NBC News poll said that in a four-way race that included Libertarian candidate Gary Johnson and Green Party candidate Jill Stein, Clinton's lead slips to a single point, 39-38 over Trump, with Johnson at 10 percent and Stein at 6 percent.

 The Post-ABC News poll showed a slightly closer race in a four-way contest, with Clinton at 47, Trump 37, Johnson 7 and Stein 3.