It isn’t as though these are weirdo, pro-abortion, pro-homosexual, libertarian pervert types, these are mainstream people, republicans that won the party primaries.
If you want to move the party even farther left, then you need to figure out how to eliminate the primary system.
Mainstream? So mainstream that they are going to lose to, in one case a very unpopular incumbent in Claire McCaskill, and in the other, losing a seat that had been held by a Republican for several decades, in a very Republican state.
I think if you poll on abortion you find being pro-life is mainstream, but being pro-life in the case of rape, being not mainstream. It’s a clear dividing line. On the left you could have the same phenomenon with being “pro-Choice” being mainstream, but partial-birth abortion being horrifying to a majority.