If the Dems can take the house they can then:
Reveal the facts on the Kavanaugh/FBI so-called investigation

Investigate the hell out of everything, keeping in mind that the Republicans have spent, at least, 100 million investigating the Clintons.

Investigate, and report, on markets, jobs, and businesses suffering due to Jackass trade policies.

Investigate the failure of Jackass appointees

ETC. (there is a LOT more!)