Billionaire Donald Trump has surged to the front of the 2016 Republican presidential nomination race, despite a campaign trail full of outrage and controversy.

According to Washington Post polling, Mr Trump is almost two times as popular as his closest rival Scott Walker, in the push for nomination. He is exactly twice as popular as Jeb Bush, George W Bush’s brother.

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John McCain was left unimpressed by Mr Trump’s remarks about his military service. Photo: Getty

But the survey was conducted from Thursday to Sunday, and the Washington Post said most of the participants were interviewed before Trump lambasted John McCain on Saturday.

Mr Trump sparked outrage over the weekend when he suggested that a serviceman who was captured could not be a real hero, in reference to Mr McCain’s time in a Vietnamese prison.

His popularity among those questioned dropped significantly after that latest outburst, the Washington Post said.

Mr McCain said Mr Trump should apologise to veterans after the comments.

While the sample size for the follow-up poll was smaller, the drop was “statistically significant”, according to the Post’s report.

However the slip in popularity hasn’t deterred Mr Trump from risky bravado on the campaign trail.

The next day he continued his abrasive push for candidacy, slamming fellow Republicans and Democrats, but also handing out a senator’s phone number.

At a rally in Sun City, Mr Trump shared the number of South Carolina senator and fellow republican candidate, Lindsay Graham.

Mr Trump said the senator phoned him in 2014 to ask for campaign donations. He then called out the number and pulled a note from his pocket with the number written on it.

According to Mashable, calling the number went straight to voicemail and callers soon were told it was full.

Both TIME and CBS News confirmed the number was for Mr Graham’s mobile phone.

Speaking on CBS Mr Graham responded: “I don’t care if he drops out. Stay in the race, just stop being a jackass.”

He then took to Twitter for some new phone advice.

Probably getting a new phone. iPhone or Android?

— Lindsey Graham (@LindseyGrahamSC) July 21, 2015

The latest controversy comes after earlier on the campaign trail, Mr Trump offended America’s sizeable Hispanic community.

He said: “[Mexico is] sending people that have lots of problems, and they are bringing those problems to us. They are bringing drugs, and bringing crime, and their rapists.”

– with AAP