that is that they don't think they can beat President Trump in the election

Based on everything leftists have said, they have everything they need to impeach President Trump except the guts to do it. Nancy Pelosi has stonewalled the crazy faction in her party. Many on their side have articulated "why take the risky step of impeaching Trump when we will just beat him in 2020"? Politically it is a sound strategy.

But..............

The two democrat party debates thus far have shown that unless something MAJOR happens the democrat party has very little chance of defeating President Trump in 2020. So if they march forward with impeachment, it will be an admission that they don't think they can win in 2020

The left attacking Obama at the debates was a bridge too far for many on the left who have now realized that they have let the crazy folk take over. But, they can't put the genie back in the bottle.