They can ask all they want. It does not mean that the answers are factual. You can be sure the more people they ask the more people will remember being there. The power of suggestion is very strong.
How the questions are worded have great bearing on the response. People want to give the “right” answer and earn approval from the questioner. Often they do not realize they are lead into giving the answer desired. Think, “Do you remember going to a party where Brett Kavanaugh was present?” vs. “Many of those we contacted remember a party where a sexual assault took place. They say that Brett Kavanaugh was probably there. Does that seem correct to you”? The first requires a simple yes or no. The second requires you accepting a scenario in your mind and deciding if it is plausible.
It is worded so you put together the two allegations; the sexual assault and Kavanaugh probably being there. Once that happens the questions will assume Kavanaugh committed the assault. This is not done by chance. In very little time the person being questioned will remember knowing about the assault. And that’s that.
Now a deposition would be another matter.
I agree, and that’s why I think making this an argument about the truth is a mistake. The argument needs to be that it is irrelevant. 35 year old high school behavior doesn’t matter (and I deny it anyway). But the focus on attacking the truthfulness and character of the accuser is going to backfire.