Dems have no power in impeachment proceedings only GOP can push since they control everything.
Impeachment is a political process beholden to public perception and trump's at relatively low approval. Not unlikely they can convince enough democrats dumb enough to hang onto the birther magnate cus don't want to hurt trumpsters' feelings.
As another example, it doesn't take degens long to figure out the rational self-interest in aligning with other degens to win elections, while the most wide eyed democrats are occupied insisting degens can't possibly outsmart their dumb/naive asses doing so. That and also busy agreeing how describing racist and greedy behavior as degenerate is unfair and mean. Not hard to figure which side underperforms in politics.