They need to get more swing seats. How to do that if you can't show people you try to fight for them?

By not forcing leadership to take unpopular positions. By not engaging in futile gestures that please your base but alienate the center.

Shutdowns are unpopular. They cause a lot of pain for people who need government services. They cause pain for furloughed government employees. They disrupt private businesses that depend on government contracts or employees to function. And they never work.

You don't win elections by showing people you're willing to fight for the unpopular position. You lose elections by doing that. It's a common tactic by the base in both parties to try to force candidates to publicly agree with them, to irrevocably demonstrate that the candidate is with them, will fight for them - because that increases the power of the base within the party. But it ends up forcing your national candidates and important party figures to publicly take unpopular positions which hurt every Democrat when they're out there trying to win swing seats.

This is exactly what Yglesias was talking about. The base wants Schumer to fight for the base, and the base wants a meaningless performative gesture of in-group signaling as a talisman of fealty. Meanwhile, the majority of the voters don't want the government to be shut down - so Schumer would be showing that he won't fight for the majority of voters against the base. It's dumb, it loses elections, and accomplishes nothing except to make the people who are mad feel a little more in control of something.

BTW, of course the GOP would love for the government to shut down. I mean, obviously at this point. The Democrats would be blamed enough so that they wouldn't get too much damage, and the benefits are utterly enormous compared to that. All the bad stuff that's going to happen to the economy, the stock market, to government services....all the FAFO consequences from the tariffs and destruction of government? The GOP would be able to blame a ton of that on Democrats for shutting down the government for a month. And it would be a month, because after 30 days the Administration gets a ton of additional powers in managing a shutdown that would allow it to fire tons of workers, not pay them back their salaries for furlough time, etc.

Yeah, one can retreat from folly without backing into cowardice. Schumer showed far more spine facing down the wrath of the progressive left than he would have if he had indulged their self-destructive impulse to engage in a massively unpopular protest.