mainly by legitimising the bourgeois electoral process as a means to achieve power against capital, which forestalls the development of revolutionary consciousness. if the DSA were more like a Bolshevik party (or a party of any kind, really) then these campaigns would be more useful bc they’d be able to dictate his moves and use him to demonstrate the inadequacy of bourgeois electoralism, but instead this campaign is leading the DSA in the direction of further participation in electoral politics as a route to achieve “socialism”.

What revolutionary capacity exists that this guy is draining?

it’s more about how over-emphasis on electoral struggles in imperial countries prevents the necessary development of revolutionary capacity. the only usefulness of these kinds of candidates is when they inevitably move into the Democratic mainstream and inadvertently disillusion a lot of people who were hoping they’d be more radical, which results in SOME of them developing more revolutionary ideas as a by-product (while pushing more of them into apathy or outright reaction)