The White House has a whole new Russia headache on its hands after Donald Trump Jr. on Sunday acknowledged he met in June 2016 with a Kremlin-tied lawyer who was pitching opposition research on Hillary Clinton.

The president's son isn't apologizing for the meeting, and the White House as a whole is taking its usually defiant tone about the whole thing. But that may prove difficult for a whole host of reasons.

Below are a number of questions that this thing demands answers to — perhaps starting with Monday's White House briefing.

1. Why is seeking opposition research from a Kremlin-backed lawyer not a Very Bad Thing — in and of itself?

Let's set aside, for the moment, that this meeting has been kept secret for so long. And let's also set aside, for the moment, that the White House has regularly denied contact with Russians and any form of collusion.

Why is this okay?

Isolated from all these other factors, this was three people very close to the then-presumptive Republican presidential nominee — Trump Jr., Jared Kushner and then-campaign chairman Paul Manafort — granting a meeting with a Russian lawyer with ties to the Kremlin for the purposes of opposition research.

Trump Jr. and the White House have repeatedly argued that nothing came of the meeting and that it turned out the lawyer, Natalia Veselnitskaya, didn't actually have useful information. But why does that even matter? Wasn't the intent to accept such information from a Russian national with suspect ties? And how is that different from the propaganda effort Russia engaged in during the 2016 campaign that is the subject of investigations?

Basically: Does the White House believe that it's actually okay to allow foreign nationals to influence American elections in this way?

Which brings us to …

2. Were there other similar contacts with Russians (or other foreign nationals)?

Was this an isolated incident, or did the Trump campaign officials engage in this kind of thing regularly? That they took this meeting and aren't apologizing for it suggests they may have been open to other, similar entreaties. So were there any?

We now know they were in the market for this brand of help. At this point, the White House should make sure it doesn't have any other such meetings or conversations with Russians.

3. How much were sanctions discussed?

Trump Jr.'s initial statement, when the New York Times broke news of the meeting on Saturday, was that the meeting was primarily about Russian adoption -- having left out any mention of the potential oppo payoff of meeting with Veselnitskaya.

That statement also suggested that sanctions weren't a significant topic of conversation. But that's somewhat difficult to believe, given Russian adoption is so inextricably tied to the sanctions issue. Indeed, Russian adoptions to the United States were halted because of sanctions -- specifically, the Magnitsky Act, a 2012 law that imposed sanctions for Russia's human rights abuses.

Michael Flynn got in trouble for talking about sanctions with Russia's ambassador before Trump was president; did Trump Jr. do this too? And what about sanctions was discussed?

4. How did President Trump not know about this?

Trump Jr. said his father “knew nothing of the meeting or these events.” But again, this was three people who were closer to him and to the campaign than just about anybody else: His son, his son-in-law who is now a senior White House adviser, and the guy who was then running the campaign.

This meeting was seen as significant enough for all three of them to make a point to attend, and yet nobody shared details of the meeting with the guy whose campaign they were acting as members of? The president is going to have to address this.

5. Why has the White House failed to get its story straight on so many occasions?

We may one day reach a point where we can say that there was no collusion or anything untoward happening between the Russians and the Trump campaign. But if that's the case, the White House has only fueled this story with its long string of tardy disclosures and contradictory denials.

The question is why? Why are we still learning about meetings between Trump associates and the Russians months after this issue first blew up in their face with the Michael Flynn situation? Why hasn't anybody done a forensic accounting of every single possible meeting between a member of the Trump team and Russians like Veselnitskaya?

When you are treading water in situations like these, the best strategy is generally to get all the bad news out at once, and to understand the truth so that you don't keep getting caught in falsehoods that make it look like you have something to hide.

There are basically two options for the White House officials here: They are trying to hide something, or they are completely derelict in dealing with — and getting out in front of — all of this.