Because the question puts Joe Biden and Kamala Harris between a rock and a hard place, and everyone knows it. Members of their own party in the Senate have floated the idea of packing the court if Democrats win the election and take control of Washington. That would require a bill to pass Congress and a president to sign the bill, and it would dramatically remake the Article III branch of government. That makes it a top-tier presidential-election issue, and Joe Biden knows it.

Last night, though, Biden refused to answer the question lest voters take that answer into consideration while voting:

WALLACE: All right. I have one final question for you, Mr. Vice President. If Senate Republicans — we were talking originally about the Supreme Court here. If Senate Republicans go ahead and confirm Justice Barrett, there has been talk about ending the filibuster or even packing the court, adding to the nine justices there. You called this a distraction by the president, but in fact it wasn’t brought up by the president; it was brought up by some of your Democratic colleagues in the Congress.

BIDEN: I’m saying…

WALLACE: So my question to you, is you have refused in the past to talk about it. Are you willing to tell the American people tonight whether or not you will support either ending the filibuster, or packing the court…

BIDEN: Whatever the position I take on that, that will become the issue. The issue is the American people should speak. You should go out and vote. You’re in voting now. Vote and let your senators know how strongly you feel. Vote now. Make sure you in fact let people know.

TRUMP: He doesn’t want to answer the question.

BIDEN: I’m not going to answer that question because…

TRUMP: Why wouldn’t you answer that question?

BIDEN: The question is…

TRUMP: The radical left…

BIDEN: Would you shut up, man?

That’s an unusually blunt way of refusing to answer a question. Essentially, Biden doesn’t want to discuss any policy, because his strategy is to make Donald Trump himself the only issue in the election. It’s a smart strategy, but this answer is terrible in that Biden makes that strategy too obvious. Americans may not like Trump, by and large, but they also don’t like buying a pig in the poke, either.

So how should Biden duck questions? He might want to take some lessons from his running mate. After the debate, CNN’s Jake Tapper tried to pin Kamala Harris down on the same issue. Rather than just refuse to answer the question, Harris instead answers her own version of the question, and runs out the clock on Tapper:

TAPPER: There are a number of Democrats in Washington, as you know, who are saying that if Judge Barrett is confirmed and if you and Joe Biden win and the Democrats take back the Senate, then there should be consideration of adding seats to the U.S. Supreme Court. Neither you nor Joe Biden are willing to give us a straight answer as to whether or not you are willing to entertain that idea. But it’s not some fringe idea. Democrats in Washington are talking about it. Chuck Schumer, the Democratic leader in the Senate, has said that he’s not taking anything off the table. Is that an idea that you are willing to think about?

HARRIS: We are 35 days away from an election that is probably the most important election of our lifetime and our children’s lifetime. And there is nothing about these next 35 days that Joe or I will take for granted. And so the focus right now is on reminding people that we have this election. It is very much in play. It is about reminding people that people are voting right now, almost 1 million people Jake in our country have already voted, we are in the midst of an election and the Republican leader of the Senate together with Donald Trump are in the spirit of hypocrisy, trying to push through a nominee while the American people are voting.

And so Joe has been really clear. Let’s focus on what is happening right now. Deal with later-later. Focus on what is happening right now, which is the American people are voting and they should be the ones to decide who will have the next lifetime appointment to the United States Supreme Court. Let’s not get distracted. Let’s be focused on what is right in front of us. Because there is a lot at stake in terms of the integrity of our democracy, of our election system and this process that should take place over the next 35 days.

TAPPER: I will respectfully note that you also declined to answer that question with me. Senator Kamala Harris, I appreciate your time this evening. Thank you so much.

HARRIS: Good to be with you, Jake. Thanks for the question.

Tapper then turned in frustration to Abby Phillip on the set, who pointed out the avoidance strategy:

TAPPER: All right, yes. So, I don’t really understand Abby why they won’t answer that question. I guess they just feel like — it’s — well, yes, I guess —

PHILLIP: I understand (inaudible).

(CROSSTALK) TAPPER: I understand, why don’t you explain for the American people?

PHILLIP: They won’t that answer that question because this is sort of like the Medicare for all of the general election. Which is that there is an idea that is being talked about on the left of their party and they want to stay in the middle. That is why they won’t answer the question.

This is an excellent analogy. Supportive talk for court-packing will scare off centrists; opposition to it will anger progressives and risk losing their engagement and energy, which are already in short supply for this campaign. It goes further than that, though, because any discussion of policy shifts the focus off of Trump and onto a five-decade denizen of DC whose track record only begun to get unpeeled by Trump last night.

If and when we have another debate, Trump has to get more focused on Biden’s policies and specifics of his track record. Every single Trump answer on policy should start off with, “My opponent has had 47 years to fix this and failed, by [insert Biden policy record here]. I have been here for 45 months, and this is what I have done.” That will take more prep than Trump exhibited last night, but the result will be much more effective. Then perhaps Trump will be in position to offer Harris’ “Thanks for the question!” after getting what he wants out of it.