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Soon after President Barack Obama endorsed Hillary Clinton, GOP presumptive nominee Donald Trump weighed in on Twitter with his characteristic brash tone.
That prompted a Twitter burn from Clinton's social media team.
That message became her campaign's most-retweeted Tweet ever, according to her team. It spawned the hashtag #DeleteYourAccount which trended Thursday afternoon. But the trolling didn't stop there. Trump and the GOP fired back, alluding to her private email server controversy.
And RNC Chairman Reince Priebus piled on.