how can the democrats impeach trump?

I understand by a simple majority. I understand this.

But if they are just talking about it, they control the narrative.

If they send it over to the senate, the senate will have authority to call witnesses and they could call whoever they want.

This one would expect could cause their entire house of cards to collapse. It in reality could make them look like total fools and the outcome could be far worse than the whole russia collusion hoax.

So, why would the dems actually impeach trump and risk all that? Is this impeachment inquiry just political theater and they will say at the end well, we are going to have an election so its not worth impeaching him?

They don't actually think they have anything, or they wouldn't control the narrative so closely. So what is their game here?

Their base is more worked up than ever, so can they not impeach? But how can they actually impeach and then lose control of the narrative?

I understand that the media will back them up but still, people are getting news from other sources now so the msm is losing its hold.

Any ideas?