I have noted that all the news reports in the last couple of days concerning their recent GAO report on the funding withheld for Ukraine begin with something like, "The Government Accountability Office (GAO) is a nonpartisan organization... Basically, here's a group not tied to one political party.
If you personally don't know who they are and why you should trust their investigations, click on the GAO link above which will give you the basics. Over the years I've had numerous interactions with the GAO and found them to be just what the news reports say, nonpartisan and pretty thorough in their work. I have shared many of their reports and findings here in this blog over the years.