Pretty small out-of-sample window, but we built a trading strategy on top of congressional trading data and it's done well since we launched it last year.

You can see the backtest performance here, but the holdings and advanced metrics are behind a paywall (apologies in advance): https://www.quiverquant.com/strategies/

As others have pointed out, there is a delay between when the trades are made and when they are disclosed and our strategy is able to act on them.

However, this is somewhat countered by the fact that politicians tend to hold stocks for long periods of time.

There are definitely some examples of politicians trading a stock right before a massive market moving event, but I think they are generally looking at a longer time horizon when they are investing.