Sen. Ben Sasse (R-Neb.) on Tuesday vowed to give up on the GOP if Donald TrumpDonald John TrumpThe Guardian slams Trump over comments about assault on reporter Five takeaways from the first North Dakota Senate debate Watchdog org: Tillerson used million in taxpayer funds to fly throughout US MORE wins the party’s presidential nomination.

“Let’s first recognize that the Republican Party is just a tool, as all political parties are,” he told hosts Joe Scarborough and Mika Brzezinski on MSNBC’s “Morning Joe."

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“I signed up for the party of Abraham Lincoln, not the party of David Duke, Donald Trump,” Sasse continued, linking the white nationalist with Trump’s White House run.

“I hope it happens over the course of the next 30 to 60 days that the Republican Party again becomes the party of Abraham Lincoln, limited government and great human potential. I want to celebrate what’s great about America in the Republican Party, but if the Republican Party becomes the party of David Duke, Donald Trump, I’m out.”

Sasse then rejected the notion that Trump could evolve into a stronger conservative.

“I don’t that this guy has any more core principles than a Kardashian marriage,” he said. "Do any of you think Donald Trump has any core values? I don’t think it’s conceivable."

Sasse additionally slammed his own party for helping fuel Trump’s popularity with voters nationwide.

“The core principles of the Republican Party have not been clear,” he said. "Ultimately, Donald Trump has seized upon a vacuous, falling-apart organization.”

Sasse has repeatedly challenged Trump’s fitness for the presidency, most recently penning an open letter late last Sunday night rejecting the billionaire’s campaign.

Trump is currently under fire for his hesitancy to denounce support from Duke, a former grand wizard in the Ku Klux Klan.

Duke urged listeners on his radio show last week to vote for the real estate tycoon, arguing that picking either Marco RubioMarco Antonio RubioThe Memo: Saudi storm darkens for Trump GOP leaders hesitant to challenge Trump on Saudi Arabia On The Money: Treasury official charged with leaking info on ex-Trump advisers | Trump to seek 5 percent budget cut from Cabinet members | Mnuchin to decide by Thursday on attending Saudi conference MORE or Ted CruzRafael (Ted) Edward CruzO'Rourke gives 'a definitive no' to possibility of running in 2020 Vicente Fox endorses Beto O'Rourke in Texas Senate race Beto O'Rourke on impeachment: 'There is enough there to proceed' MORE instead denotes “treason to your heritage."