Sounds to me like they are having "propaganda remorse". You can imagine what they are saying to themselves, "wait a minute, if Trump is impeached, who becomes President?" Oh sh__, it's Pence!"
If they don't like Trump who is at least willing to bend on policy, they sure as hell are going to view a strong, Conservative like Pence as their worst nightmare. It was all fun and games when they could place Comrade Clinton or Sanders in the WH, a totally different story with Pence.
In the end, Trump isn't going anywhere. He doesn't quit and he reiterated that stance today in his speech to the Coast Guards. He's soldiering on in this political muck whether the alt-left like it or not. This is one of the biggest reasons his supporters stick with him through thick and thin, they want to address what ails America and the establishment will not and have not unfortunately. They realize he has the courage to see it through.