 -- Republican presidential front-runner Donald Trump says that he thinks comparing the tone of his campaign to that of Adolf Hitler is "terrible."

"It’s a terrible comparison," he told ABC News' George Stephanopoulos on "Good Morning America" today, adding that he hadn't heard of the comparison yet. "I’m not happy about that, certainly. I don't want that comparison."

Mexican president Peña Nieto Monday likened Trump's campaign tone to those of Adolf Hitler and Benito Mussolini during their rises to power. Comedian Louis C.K. and conservative journalist Glenn Beck have also compared the real estate mogul to Hitler in recent days.

Trump has also asked his supporters at rallies to raise their hands to pledge to vote for him, which some have compared to a Nazi salute.

When asked whether such comparisons signal that he should tone down his rhetoric, Trump said "maybe so," but added that he continues to see strong support in recent polling and at the ballot box.

Trump also pushed back against GOP establishment efforts to block him from the nomination.

"They’d rather not see me in there, obviously," he said, adding that Mitt Romney's failed 2012 challenge to incumbent President Obama was one of the worst campaign he has ever witnessed. "I would imagine something like [those attacks] could have an impact, but we have a lot of loyal people."

In response to Michael Bloomberg’s opting not to run for president because of its potential to boost Trump's candidacy, the GOP front-runner said the former New York City mayor used to be a friend.

"I guess he disagrees with what I’m saying, but a lot of people agree with what I’m saying," he said.