Presumptive Republican nominee Donald Trump has received his first un-endorsement as the firestorm expands over his racially-focused attacks on a federal judge.
Sen. Mark Kirk, Republican of Illinois, released a statement Tuesday saying that Trump lacks "the temperament" necessary for the Oval Office.
"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.
Kirk is running for re-election in what is considered one of the most contested races in the country.
Before Trump earned the nomination, Kirk said that he "certainly would" support him if he won the nomination.
But Trump's latest attacks against Judge Gonzalo Curiel, who is overseeing a suit against Trump University, is a bridge too far, Kirk says.
"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."
While Kirk is the first candidate to take back his support, he is one of more than a dozens of Republican leaders who have denounced Trump's latest comments against Curiel.
On Tuesday alone, the top Republican in Congress had harsh words for Trump. House Speaker Paul Ryan called them "the textbook definition of a racist comment" and Senate Majority Leader Mitch McConnell advised Trump to "stop attacking ... various minority groups ... and get on message."
This article originally appeared on NBCNews.com.