This article has been updated to reflect news developments. Now that House Speaker Kevin McCarthy has been tossed aside, one possible choice to replace him is Steve Scalise, the Louisiana Republican who once reportedly described himself as “David Duke without the baggage.” Scalise is an archconservative who in 2002 spoke to a white supremacist organization founded by Duke, a former grand wizard of the Ku Klux Klan. The congressman is also, thus far, the closest thing Republicans have to an establishment candidate. He “understands what people in moderate districts need,” Anthony D’Esposito, a Long Island Republican who represents a district...