GOP pollster Frank Luntz tweets some 'real talk' analysis after Hillary Clinton's big DNC speech

Republican pollster Frank Luntz did some "real talk" on Twitter on Thursday night after Hillary Clinton delivered her big speech at the Democratic National Convention.

Luntz said on the social-media platform that he was impressed with the speech from the Democratic nominee, even though he conceded that "Republicans won't like" it.

"That was the most effective speech I've ever seen from Hillary Clinton," Luntz tweeted.

He added: "Republicans won't like Hillary's speech, but the content, language, and delivery will have an impact on undecided voters."

Luntz, who accurately predicted after the Republican National Convention that Trump would take a lead in the polls in the days that followed, told his followers to "expect significant style changes" from the GOP nominee "before the first debate in 60 days."

Clinton and Trump are set to face off for the first general-election debate on September 26 at Hofstra University in New York.