Washington (CNN) Four red-state Democrats refused President Donald Trump's invitation to attend his Supreme Court nominee announcement Monday night at the White House, according to their offices.

Democratic Sens. Heidi Heitkamp of North Dakota, Doug Jones of Alabama, Joe Manchin of West Virginia and Joe Donnelly of Indiana were invited for the announcement.

"Sen. Heitkamp was invited but isn't able to attend tonight," her spokesperson said in a statement. "She has made clear -- as she said to the President in person two weeks ago -- that she considers fully vetting Supreme Court nominees one of the most important jobs of any U.S. senator, and she plans to fulfill that critical duty."

Manchin's spokesperson also said he wasn't planning to attend and the senator said later in a tweet that he appreciated the invitation from Trump.

"I appreciate the President inviting me to attend tonight's announcement at the WH," Manchin said in the tweet. "I look forward to meeting the nominee in a setting where we can discuss his or her experience, judicial philosophy & perspective on access to healthcare for WVians with pre-existing conditions."

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