After a tough summer at the ballot box for members of the so-called “Squad,” the group of progressive and diverse House Democrats is facing its final intraparty challenge on Tuesday as four states in the Midwest and New England hold primary elections.Rep. Ilhan Omar of Minnesota faces voters one week after her fellow Squad member, Rep. Cori Bush of Missouri, lost her bid for re-nomination and nearly two months after another Squad member, Rep. Jamaal Bowman of New York, fell to his primary challenger.But Omar, who made history as the first Somali American in Congress and the first woman of color to represent Minnesota on Capitol Hill, is the favorite as she faces three primary challengers in the Democrat primary. Omar is seeking a fourth two-year term repr …