Trying to drag Stevens over the finish line (and likely failing) will almost assuredly also cost Democrats at least one of Iowa, Ohio, Maine, or Texas from the funds they'll have to divert. This was never about keeping Michigan's seat centrist; it's about keeping the Senate in Republican hands.
Thomas KIf Stevens wins the Michigan primary, the DSCC will divert all money to Michigan and leave Maine, Iowa, Georgia etc Democrats to fend for themselves.