Trump rips Romney after 'trickle down bigotry' comments: He 'choked like a dog' against Obama
2012 GOP presidential nominee Mitt Romney, businessman Donald Trump -- Screen shots

2016 presumptive GOP presidential nominee Donald Trump is not taking criticism from the GOP's 2012  presidential nominee lightly, hammering back at Mitt Romney over his "trickle down"comments on Friday.

Romney blasted Trump on CNN Friday saying, "Presidents have an impact on the nature of our nation, and trickle-down racism, trickle-down bigotry, trickle-down misogyny, all these things are extraordinarily dangerous to the heart and character of America.”

Trump returned fire on Twitter, of course.

"Mitt Romney had his chance to beat a failed president but he choked like a dog. Now he calls me racist-but I am least racist person there is," he wrote.

Romney has moved to the forefront of the #NeverTrump campaign, telling CNN's Wolf Blitzer, " “My responsibility is to express to the American people what I believe is right about the potential nominee of the party. I did so very plainly and clearly, and the people who made the choice decided to go a different direction. That’s their right. But as an individual I simply can’t put my name down as someone who voted for principles that suggest racism or xenophobia, misogyny, bigotry, who’s been vulgar time and time again.”

This weekend, Romney is hold a brainstorming session in Park City, Utah, where reportedly House Speaker Paul Ryan was lambasted for supporting Trump -- with HP CEO Meg Whitman comparing Trump to Adolf Hitler and Benito Mussolini.

According to the Washington Post, Ryan was uncomfortable with the criticism and explained that, as the Speaker,he has been placed in a  tough position having to to defend the new face of the party.

Trump's tweet below: