Majority Forward, a super PAC aligned with Senate Democrats, is running an ad that says: 'Getting rich from insider trading should be illegal, but Susan Collins doesn't think so. Susan Collins is trying to keep it so senators can get rich playing the stock market' [1]. FactCheck.org reviewed it and rated the claim false [1].
The ad has the record backwards. Insider trading is already illegal for members of Congress, and it is illegal in part because of a law Collins helped write. She co-authored the 2012 STOCK Act, signed by President Obama, which made explicit that members of Congress are not exempt from insider-trading law and required faster disclosure of their trades [1]. A senator who co-sponsored the law affirming insider trading is illegal is a strange target for the charge that she thinks it should be legal.
There is a real disagreement underneath the ad, and it is worth having. Collins opposes proposals to bar members of Congress from trading individual stocks at all, favoring instead enforcement of the current rules and having any holdings managed by independent advisors [1]. Reasonable people think an outright ban is the only fix, and they can point to the STOCK Act's weak enforcement to argue it: the Campaign Legal Center notes violations often draw fines as low as 200 dollars, sometimes waived [1]. That is a legitimate critique of Collins's position. It is also not the one the ad made.
The distinction matters because it is the whole difference between disagreeing with a senator and inventing a position for her. 'Collins opposes a full ban on congressional stock trading' is true, and voters can weigh it. 'Collins thinks insider trading should be legal' is false, and it asks voters to weigh something that never happened. An attack can be tough and fair at the same time. This one traded the fair version for a false one, and our job is to say so no matter which side runs it.