Freshman Rep. Rashida Tlaib’s Twitter bio declares her the “Unbossed Congresswoman” for Michigan’s 13th District. While the moniker has roots in Shirley Chisholm’s successful campaign to become the first black congresswoman, nowadays it also could be seen as a blunt message to Democratic leadership: Nobody is bossing around the class of 2019. And that’s a problem for party bosses. On everything from the Green New Deal to impeachment to criticism of Israel, a squad of first-year congresswomen are flexing their muscle and posing an implicit challenge to Democratic honchos like Speaker Nancy Pelosi. Their stridently liberal agenda – and power...