Pop-up super PACs flood primaries with undisclosed donors

Outside groups are increasingly using ‘pop-up’ super PACs that can raise and spend unlimited money in the final days of primaries without disclosing donors until after the election, flooding races with roughly $48 million so far this cycle; the tactic exploits FEC timing, raises concerns about transparency, and has seen groups tied to Republicans and to AIPAC influence races; lawmakers are proposing tighter disclosures, including a bill to require reporting large donations in the last 20 days of an election.