As I explained in the blog, the primary is affected by saying our only qualification for a candidate is that he can beat Vance. Admitting that up front trends you towards someone that appeals as much as possible to Vance voters and takes Democratic Party voters for granted.
Also as mentioned in the blog, you are not simply voting in one election and that's the end of it. This is an iterative negotiation and so doing lesser evil in one election causes things to swing more evil in the next election. That's how you go from the Republic Party winning with a Reagan to the Democratic Party potentially nominating an economic policy Reagan clone to beat Vance.