I don't think there's an exception to the insider trading rules relating to "impact on financial circumstances". But maybe there is for being in congress. I don't follow the exceptions for congress stuff very carefully.
If the rules are the same for pols, then you trade on insider information, you have committed a crime. All of the pieces of an insider purchase are present: an insider; the claim to have provided the tip; the subsequent purchase; the profit. And the double-whammy of front-running the legislation.
Not saying he transgressed. But you have to waive aside a few coincidences to assume his innocence.
You may be right that the Dems are stirring the pot. Haven't been watching so cannot say.