Washington (CNN) The resignation of White House staff secretary Rob Porter after accusations that he abused both of his ex-wives raised lots -- and lots -- of questions about who knew what and when, and why no one acted before pictures emerged of his then-wife with a black eye.

Below are six questions the White House needs to answer about this whole mess.

1. Who knew about this?

We know from CNN reporting that "senior White House officials" -- including chief of staff John Kelly -- knew the basic outlines of the allegations against Porter. Who other than Kelly knew? And what, if anything, did they say or do? Kelly, we now know, pushed Porter into ever-more important roles within the Trump inner circle despite knowing the allegations. Did Kellyanne Conway know? Jared Kushner? Ivanka Trump? And did any of them do anything other than go along with Porter's ascension in Trumpworld?

2. What did Kelly know -- and when?

It's clear that Kelly was aware of the accusations against Porter as far back as last fall. But what, exactly, did he know? And when did he learn the severity of what Porter is alleged to have done? Kelly loyalists sought to cover for the chief of staff on Wednesday night, insisting that he was taken aback by the picture of one of Porter's ex-wives with a black eye -- and that no one, Kelly, included, knew the extent of what was being alleged until the past 24 hours. But there are conflicting reports as to what Kelly knew and when he knew it.

The problem with any of the explanations is that even after the story of Porter's alleged abuse came out in the Daily Mail earlier this week, Kelly continued to urge Porter to stay on in his current role. And, even in his clean-up statement on Wednesday night, Kelly refused to walk back his praise for Porter.

3. Did the FBI alert the White House to Porter's issues? And when?

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Both of Porter's ex-wives talked to the FBI about the alleged abuse as part of his background check. Did the FBI alert Kelly -- or anyone else in the White House -- to the seriousness of the allegations? Is that how Kelly and the other senior White House staffers knew about it? If not, why not? And if the FBI did warn Kelly about the accusations, why was Porter not only kept on but brought even closer into the inner circle? Even if Porter was telling his colleagues that the whole thing was simply an attempt by his exes to smear him, wouldn't a warning from the FBI trump that? Or, put differently: Shouldn't it?

4. How was Porter doing his job without a full security clearance?

Don't be fooled by the job title. "Staff secretary" to the President of the United States is a hugely important job. That person is a direct conduit to the President, traveling with him and serving as a sort of information gate-keeper. That role with a President like Trump is even more important, and Porter's ability to effectively manage the information flow to Trump made him invaluable to Kelly.

But how can someone in that senior a position not have a full security clearance? It's been a year. Wouldn't that raise some red flags for Kelly and others in the White House? And how, logistically speaking, could Porter do his job without a security clearance?

5. Why was Hope Hicks involved in crafting the Kelly statement?

Hicks and Porter are romantically involved. Which makes it very odd that she was part of a small group tasked with writing a statement from Kelly that offered a full-throated defense of Porter.

This is that statement: "Rob Porter is a man of true integrity and honor and I can't say enough good things about him. He is a friend, a confidante and a trusted professional. I am proud to serve alongside him."

It's that statement that Kelly kind of, sort of walked back on Wednesday night. But couldn't anyone see how Hicks writing it might be sort of a conflict?

6. How much did Trump know and how did he react?

According to CNN reporting, Trump was informed of the allegations around Porter earlier this week when the Daily Mail story broke. But, what, exactly was he told? And, what was his reaction? Did he support the full-throated defense of Porter from Kelly? Did he even know about it? Did he urge Kelly to have that response? Or did Trump want Porter out? If he did, why didn't it happen? (Remember that Porter resigned. He wasn't fired.)