No one has done as much damage to the Republican Party or the Constitution as John McCain. He continually attacked the Republican Party conservatives and sided with far left Democrats to get his left wing bills passed. History is the best teacher and indicator. McCain would do greater damage to a Trump administration than Kirkpatrick could ever dream of. I believe we would even have more influence over her than McCain. McCain certainly paid no attention to our wishes during his previous years in office. Kirkpatrick would have neither the seniority or influence to do the damage that McCain has already caused. McCain's defeat would create new life in the conservative wing of the Republican party. It is just about finished now.
You have 4 choices
1. Vote McCain for him to continue his attacks on the country.
2. Do not vote in the Senate contest. will hurt McCain
3. Vote for anyone you choose to. They will not win, but it will hurt McCain.
4. Vote for Kirkpatrick which will hurt McCain the most. And she will be in no position to hurt Trump as much as McCain would.