When you “build a public record” in a committee hearing, what you are trying to do is shape future political action and future political assessments. In a hearing about potential legislation, you are trying to build media coverage, raise public awareness, compel stakeholder or public official interest, and/or signal your intention to commit resources.
This is all done in order to affect future political action by others: to build your coalition of support, or maybe convince opponents to back down, or to try to put the issue onto the policy agenda of congressional leaders, force intervening action in the executive branch or private sphere, or setup issues for an election. Or all of the above. Ditto with an oversight or investigative hearing.
Even more importantly, you build a public record so that you shape the public understanding of what you are doing. Actions taken by public officials don’t occur in a vacuum: they occur in the public sphere. How the public comes to understand those actions has enormous political ramifications: for the parties, for individual members, and for public policy.
An action that would be controversial absent an explanation can become a good and reasonable thing to do; likewise, an action that would not be controversial can become a rash and dangerous thing. All depending on how the public comes to understand the action.
At it’s political core, the Judiciary committee confirmation hearing of Judge Brown Jackson isn’t about whether or not the Senate should confirm her to the Supreme Court. That’s pretty much been decided—the Senate will confirm her nomination.16 What is at stake in the hearing is the public understanding of what that confirmation means. You can’t think of a court confirmation as a black or white, confirm or reject. What is still up in the air is the ultimate public meaning of these events. That’s the fight.17