Here are the 5 best 'Berns' of the GOP presidential field -- so far

Bernie Sanders doesn't do negative campaigning. In his decades of public service, he has never run an attack ad.

He does, however, believe in challenging the views of his opponents. Throughout the course of the campaign, he has distinguished his own worldview from that of Republican presidential hopefuls. Here are some of his best “berns” of GOP frontrunner Donald Trump and other GOP candidates.

1. Condemning Trump's Bigotry

Trump has made bigoted statements on numerous occasions to bolster his presidential run, and by August, Sanders had had enough.

"I think Donald Trump's views on immigration and his slurring of the Latino community is not something that should be going on in the year 2015,” he said. “And it's to me an embarrassment for our country.”

2. Defending America's Religious Pluralism from Ben Carson

When Dr. Ben Carson said a Muslim should not be president, Sanders condemned him.

"This is the year 2015. For a long, long time in the history of America, there were people who would say, 'You know, we don't want a Catholic to be president of the United States.' And then John F. Kennedy became president in 1960," Sanders said. "And then people said, 'Oh, we don't want a black guy, [an] African American, to be president of the United States,' and then finally Barack Obama became president of the United States. Look, you judge candidates for president not on their religion, not on the color of their skin, but on their ideas on what they stand for. That's what democracy is supposed to be about. So I was very disappointed in Dr. Carson's statement, and I disagree with him."

3. Calling Out Jeb Bush's Insults Toward African Americans

Jeb Bush said that he didn't want to offer “free stuff” to African American voters. Sanders hit back on Twitter that this was “pathetic. @JebBush wants more tax breaks for his billionaire friends while cutting help for working people.”

4. Summarizing GOP Hate

Shortly after Bush's comments, Sanders summarized how his opponents seem to be avoiding the issues and just engaging in divisive hate by tweeting: “Can't @JebBush and the GOP run a campaign without attacking African Americans, Latinos, Muslims or other people?”

5. Going to Town on the GOP Debates

During the two GOP debates that have taken place so far, Bernie Sanders decided to live-tweet his own reactions to their remarks. Many of his responses had to do with how disconnected the debates were from the concerns of ordinary Americans: “Waiting, waiting, waiting. Will we hear anything about racial justice, income inequality or making college affordable?” Others had to do with poking fun at  frontrunner Donald Trump's lack of humility: “Trump. What a pleasant and humble person. Can't stop saying kind and generous things about his fellow Republicans.” And there was also his derision of their foreign policy views: “War, war, war. When do we get to their other major priority: tax breaks for billionaires?” His final tweet of the second debate, sent half an hour before it ended, had a bite: “Thank you all. I've had it. I'm going home. Talk to you soon.”

Sanders is known for running positive campaigns. But as his performance so far has shown, that doesn't mean he isn't willing to show Americans what's wrong with the worldview and actions of his opponents, and he has delivered some of the election season's most memorable Berns.