Understand that when your goal is blocking things, you somstimes do things you know will almost certainly fail. Republicans have used this playbook for ages to block the Democratic party
Make them get tied up in as many pointless tasks to distract them from their other goals. Sometimes you'll even occasionally win a long shot challange
Start at the local level and build up. It's a lot easier to have strong progressives run in races that might not really be all that contested in the first place. And make even small primaries count
That kind of power starts to add up. The local politicians tend to flow up the party. Obama first rose from the Illinois state senate. Tim Walz first rose from an unexpected flip in a deep red house district in Minnesota
Power doesn't always flow top down. It also flow from the bottom up