Hillary Clinton on Wednesday afternoon said she “could not even imagine the grief and the heartbreak” Joe Biden has suffered from personal tragedies in his life, a preview of just how difficult it could be for Clinton to attack the vice president if he decides to challenge her for the Democratic presidential nomination.

Clinton said she has had no private conversations with Biden as he weighs a presidential campaign, and that neither she personally nor any of her campaign operatives have received any behind-the-scenes briefing on Biden’s thinking process from any of his top aides.

“I haven’t asked for that,” Clinton told reporters at a brief Q&A after a campaign stop outside Des Moines. “I just want the vice president to do what’s right for him and his family. I don’t think it’s useful to be behind the scenes, asking this or saying that. I’ve done none of that. I just want him to reach whatever the right decision is.”