By Arun Kumar 

Washington, Aug 20 (IANS): Fast closing the gap with Hillary Clinton, Republican presidential front-runner Donald Trump says the controversy surrounding his Democratic rival's use of a private server for official emails is "devastating."

"I think it's devastating for the election, but I think her bigger problem is not the election. I think her bigger problem is going to be the criminal (problem)," he said after a CNN/ORC poll showed him within striking distance of the former secretary of state.

Trump, who has quickly leapt to the top of the crowded Republican field, told CNN that it's not surprising that he came within 6 points of the leading Democrat (45 percent to 51 percent) in a head-to-head polling match-up for the 2016 race for the White House.

Clinton is not his "focus right now," he said, but predicted she would struggle to get over the bad headlines generated by the investigation into her private server and the possible transmission of classified information in her private email.

Even the money she has raked in for speeches since leaving office in 2013, he said.

"I think that Hillary's going to have a hard time being in the election based on what's going on with the emails, the servers, maybe even the speeches," Trump said. "I think it's going to be a very hard thing for her to overcome."

Trump compared Clinton's situation to that of Gen. David Petraeus, former Director of the Central Intelligence Agency, who pleaded guilty to giving some classified information to his biographer and lover.

"When I look at what happened with Petraeus ... great general, wonderful guy, everybody loved him, and it destroyed his life over much less," Trump said.

"It would seem hard to think that somebody could have a much worse situation than him and escape."

He acknowledged that the Justice Department investigation hasn't named Clinton, but he said he believes what she did was criminal.

"It certainly looks like it was high-level information," Trump said. "It's always skirting the edge. What's the purpose of it? ... What is she doing, why is she doing it?"

"I don't think I'm the only one. The FBI's involved, they only do criminal," Trump said.

"Now maybe it's somebody on her staff. But look, it's ether criminal or incompetent, it's one or another ... either gross incompetence or criminal, and neither's acceptable to be president."

Clinton has sought to downplay the email story saying it was "political” and "has nothing to do with me." She even made fun of questions about whether she "wiped" the server and said "no one" asks her about the emails and the servers but the press.