She knows.

Hillary ClintonHillary Diane Rodham Clinton Democrats plot new approach to win over rural voters The Memo: Sanders-Warren battle could reshape Democratic primary Rosenstein says he authorized release of Strzok-Page texts MORE is staring defeat in the face. It doesn't mean she is going to lose, but as she trudges up that ever-so-steep hill to win the Democratic nomination, she is beginning to weigh Plan B.

Clinton hears the voices, not of those people who need to be heard in those 10 remaining contests she keeps talking about, but the ones from her own supporters who are sounding increasingly doubtful about her path to victory. Supporters and allies like New Jersey Gov. Jon Corzine (D) and Rep. John Murtha (D-Pa.) are saying Clinton needs to win the popular vote. Now her new pollster, Geoff Garin, said in his first interview: "I don't want there to be a thermonuclear climax," and he put heavy emphasis on party unity. Does that sound like someone hired to fight to the convention floor?

Rep. Rahm Emanuel (D-Ill.) said he thinks it will be clear on May 6, after Indiana and North Carolina. These are the types of comments that didn't go on the record just weeks ago. But the window is closing. In my column this week, I described why both Bill and Hillary Clinton have to already be pondering and planning for the rehabilitation and reconciliation that would follow defeat.

Yes, she could still win landslides in Pennsylvania and the rest of the primaries, clean up in popular vote and win the nomination by superdelegates. Raise your hand if you see that happening. The Clintons are stubborn, but they are not stupid. They are having this conversation, too.

Before the public sees you throw in the towel, you practice throwing it privately a few times first.