I believe you're underestimating the lag inherent in the economy. Even if we grant the idea that the political party controlling the US House/Senate has a significant impact on the economy, and that the current party is BAD and the next one would be GOOD, I would still expect that things will continue getting WORSE for a good 4 to 8 years before they get better again.

And that's even with assuming that we can continue to ignore the long-term problems like social security insolvency, the debt bomb, or climate change forever.