Senate Democrats were surprised to hear of United Nations Ambassador Nikki Haley’s sudden resignation on Tuesday, but many held their fire when asked about possible replacements for the post.

Following Haley’s announcement, President Trump floated his daughter, Ivanka Trump, as a possible candidate but admitted nepotism laws would make such a nomination difficult. Within hours, Ivanka said the "replacement will not be me."

Democrats didn’t want to comment on who could replace Haley, nor commit to fighting the ultimate nominee, but expressed disappointment that the former South Carolina governor decided to step aside.

[Read: The top 10 contenders to replace Nikki Haley at the UN]

“She was one of few voices in the administration talking about democracy and human rights,” said Sen. Chris Murphy, D-Conn., “I shudder a little bit to think of who’s coming next.”

Murphy said he expects national security adviser John Bolton will try to influence Trump’s decision and advocate for a “traditional neo-con” in Bolton’s image.

“That scares me,” Murphy said.

Still, Murphy said he’d wait to see who Trump nominates, adding that he hopes Secretary of State Mike Pompeo has “significant influence” over who is ultimately picked.

Democratic Sens. Brian Schatz of Hawaii, Claire McCaskill of Missouri, and Tim Kaine of Virginia all said they were surprised, but refused to comment more on the news.

Sen. Jeanne Shaheen, D-N.H., said she hopes whoever is nominated will “fight for human rights and democracy” for everyone in the world.

“I voted for her; I think she’s done an incredible job,” said Senate Minority Whip Dick Durbin, D-Ill. “I sometimes struggle to understand this administration’s foreign policy, but I think she’s been an articulate and forceful spokesman.”