Not necessarily - Bernie Sanders runs as an independent and just caucuses with the Democrats (same for Angus King, the other independent in the Senate, although

Not necessarily - Bernie Sanders runs as an independent and just caucuses with the Democrats (same for Angus King, the other independent in the Senate, although he's not of the DSA). However, it doesn't look like anyone in the House is an independent, so maybe Bernie's the only one that does that.