Texas Attorney General Ken Paxton, who’s a Republican candidate for the U.S. Senate, says his office is planning to launch undercover operations targeting liberals. The scandal-plagued Paxton has incentive to carve a lane for himself as the Trumpiest candidate in the primary. Last year, he reached a deal to avoid a securities fraud trial and avoided removal from office after being impeached over corruption allegations. That’s helpful context for his conspiracy theory-filled announcement of undercover investigations into liberals, which he said will complement President Donald Trump’s efforts to use federal agencies and the military against antifa. That Paxton announced these...