Wall Street’s exchange-traded fund factory has spent the year testing how much it can push boundaries, but some ideas proved a step too far. With more than $1.4 trillion flowing into ETFs last year, issuers have rolled out products that dial up leverage and chase mouth-watering yields. Connecticut-based Tuttle Capital Management recently pitched an ETF built around a provocative premise: that political influence itself can be an investable signal. The firm’s proposed Government Grift ETF, with the propose ...