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Sen. Ben Sasse (R-Neb.) ripped Republican presidential candidate Donald TrumpDonald TrumpObama quiet on final full day in office Warren burns Mnuchin over failure to disclose assets What we learned from Rick Perry's confirmation hearing MORE on Twitter Sunday night, saying the front-runner is trying to divide the nation rather than build it back up.
Sasse tweeted that if there were a matchup between Trump and Democratic presidential candidate Hillary ClintonHillary Rodham ClintonAppeals court upholds ex-coal boss’s conviction Trump is leader millennials have been waiting for. Even if they don't know it. Sanders backers take over California Democratic Party MORE, he wouldn't support either of them. If that's the case, Sasse said there needs to be another option.
"If Trump becomes the Republican nominee my expectation is that I'll look for some 3rd candidate — a conservative option, a Constitutionalist," he tweeted.
Sasse also called out Trump for refusing to condemn the KKK during an interview Sunday morning.
"A presidential candidate who boasts of what he'll do during his 'reign' & refuses to condemn the KKK cannot lead the conservative movement," he tweeted.
Sasse said during his tweet storm that he's not an establishment Republican, while touting his record as the "4th most-conservative voting record in the Senate."
He then continued to slam Trump, saying the front-runner is focused on "dividing Americans & on tearing down rather than building back up this glorious nation."
"We can do better," he tweeted.
Sasse also said Trump doesn't understand the three branches of government and uses the word "reign" like "he thinks he's running for King?"
He called on people to stop supporting the GOP if it is no longer working to defend life, religious liberty and the Second Amendment.
The senator posted an open letter to Trump supporters on Facebook in which he said people have a right to be angry, but he emphasized that Trump is not the right candidate.
Sasse has criticized Trump in the past. He posted a video of insults he received after slamming Trump.