CHICAGO (CBS) — Republican Illinois Sen. Mark Kirk, facing a fight for his political survival, has withdrawn his support for Donald Trump’s presidential bid.

Kirk is locked in a heated fight for his U.S. Senate seat against Democratic rival, U.S. Rep. Tammy Duckworth.

Kirk also split with Republican leadership over President Obama’s Supreme Court nominee, Merrick Garland, saying the Chicago area native should get a confirmation hearing in the Senate.

Kirk earlier had said he would support the presumptive GOP presidential nominee. In May, he told CNN Trump might help his re-election effort.

“After much consideration, I have concluded that Donald Trump has not demonstrated the temperament necessary to assume the greatest office in the world,” Kirk said in a statement.

But Trump’s latest attacks against Judge Gonzalo Curiel, who is overseeing a suit against Trump University, changed Kirk’s mind.

“As the Presidential campaign progressed, I was hoping the rhetoric would tone down and reflect a campaign that was inclusive, thoughtful and principled. While I oppose the Democratic nominee, Donald Trump’s latest statements, in context with past attacks on Hispanics, women and the disabled like me, make it certain that I cannnot and will not support my party’s nominee for President regardless of the political impact on my candidacy or the Republican Party.”

Duckworth responded: