If there is ever a demand for impeachment coming from the Democrats, the Establishment Republicans will simply quash any such movement. What would be effective is what happened in August of 1974, when a delegation of Republican Senators and Congressmen marched down Pennsylvania Avenue and confronted Richard Nixon directly, demanding he resign. Nixon chose to resign, rather than take a chance with impeachment (which has proved to be an very ineffective way to remove a President).
But Democrats have far too little gumption or conscience to ever take such a step.
Good analysis