Having a special counsel works for and against both Republicans and Democrats. Mueller works in secret so this will eventually lessen the daily "leaks" about "investigations" and give Trump and the Republicans an opportunity to advance their agenda without disruption-- a big plus for them. The Democrats get the neutral party they wanted, but they also surrender control and lose the media splash they liked-- secret investigation will do this-- a big loss to the Democrats of the negative press on Trump which they enjoyed.