They want by simply winning one election. You have to build over time to achieve your goal, which means you have to show up and win as many elections as you can. Even the boring mid term ones or the ones where your candidate isn’t the most progressive or charismatic and gives you the warm and fuzzies.

50 senators isn’t a super majority, it is the smallest majority one can get so thinking any major reform like SCOTUS expansion or an abortion protection law passed with a coalition of 46 Dems, 2 independents, 1 libertarian, and one purple Dem senator is setting yourself up for disappointment.