A major antitrust bill to rein in Big Tech is poised to be reintroduced in Congress – but insiders fret that key Democrats with cozy ties to Silicon Valley could undermine their own party’s agenda. Rep. Jerry Nadler (D-NY), the top Democrat on the House Judiciary Committee, is leading a push to resurrect the American Innovation and Competition Online Act. The bill would block Big Tech firms from “self-preferencing” their own services — for example Google promoting its shopping tool in search...