Well you certainly don't fire an employee and replace them with any even more incompetent one (dem)! That's Comparative Politics 101 and basic logic.
Your analogy doesn't hold up very well because you are not the sole employer and able to pick a replacement. There are not a large field of candidates to choose from but rather a very small number who decide to run. So what happens is you try to influence others in the mob to vote for the better candidate and ensure the less competent one doesn't get in.
The other point I'd like to make is I don't want Democrats to take the House, Senate, and Presidency. I do want them to take one of them because one party in control of all three has been nothing short of a disaster.