Did President Trump defame President Obama? Not that the latter would ever sue his successor, but thinking about the merits of such a libel suit provides a useful framework for evaluating the propriety of Trump's tweets.

Here are the facts: On March 4, starting at 6:35 a.m., Trump sent six successive tweets, five concerning Obama, including this:

Where a president has no such power, Trump was accusing Obama of committing a crime, arguably damaging Obama's reputation. Not that Trump thinks much of the way Obama is regarded - he also tweeted that the 44th president is a "Bad (or sick) guy!"

In our legal hypothetical, Obama has a high bar. As a public figure, he'd have to establish actual malice - a showing that Trump had knowledge of falsity or acted with reckless disregard for the truth. Proving that Trump knew his assertions were false when he tweeted that morning from Mar-a-Lago would be extremely difficult to establish without some direct evidence, but not so when it comes to showing reckless disregard for the truth.

Trump could simply have called his intelligence chiefs to see if he was correct before touching the keypad on his phone that morning, as confirmed by my exchange last week on CNN with Gen. Michael Hayden. I said: "Imagine that you're still running the CIA or you're still running the NSA and President Trump calls and says, 'General, I need to know, was the Trump Tower surveilled?' Could you answer that question?"

Said Hayden: "Of course I could. And then if he had the follow-on question - Was there any incidental collection and did you unmask any identities? - I could answer that question too, because, Michael, I have."

Hayden was prescient in predicting to me that Trump would soon seek to criminalize the collection of incidental intelligence. Four days later, that is exactly what occurred when Rep. Devin Nunes (R., Calif.), the chair of the House Intelligence Committee, hurried to the White House to confer with Trump.

But Trump didn't avail himself of the nation's intelligence before speaking out against Obama. Instead, he relied on the conservative media. We know this in part because last week in defending his boss, Sean Spicer spent nine minutes quoting a long list of mostly friendly news sources that have reported in varying degrees about theories of the government having surveilled Trump or people close to him.

None of that information is coming into evidence in our hypothetical. It's all hearsay. Ironically, many relied on anonymous sources of the kind Trump has often railed against.

Star witnesses in this civil suit would surely include FBI Director James Comey and the head of the NSA, Adm. Mike Rogers. Testifying before Congress last week, neither supported Trump's assertion against Obama. "I have no information that supports those tweets," Comey told Adam Schiff (D., Calif.), the ranking member of the House Intelligence Committee. James Clapper, the former director of national intelligence, would also be a crucial witness. He has similarly said that no FISA warrant was issued on his watch for such a wiretap.

Then there are the Brits, whose prime minister, Theresa May, had a spokesperson issue a statement saying the claim that their intelligence aided Obama in tapping Trump was "ridiculous." (When I asked Hayden whether it was conceivable that the British equivalent of the NSA would get a telephone call from an American president, who says, "Please tap the phones or the office space of someone running for president," and oblige, he said: "Michael, I'm sorry. I'm trying to suppress a laugh here.")

And of course, Obama himself could be an effective witness. We know from a statement issued by his spokesperson that he claims to have never ordered the surveillance of a U.S. citizen.

So what defense to defamation might be offered by the defendant, Donald Trump?

Before last Wednesday, it was hard to foresee any admissible response apart from his own. But now Trump surely thinks he has a surprise witness in Nunes, who had earlier said he didn't think there was an actual tap of Trump Tower, but now asserts that Trump and/or his closest associates may have been "incidentally" caught in surveillance by U.S. intelligence of foreign nationals. That could be compelling coming from him, only that isn't what Trump asserted in his tweets. Instead, he said that Obama had his "wires tapped" in Trump Tower, and even Nunes said he is without evidence of Trump being directly wiretapped.

Nevertheless, Trump said he felt "somewhat" vindicated by Nunes' unnamed sources. And in an interview with Time, Trump drew attention to the punctuation of his tweets, saying, "When I said wiretapping, it was in quotes. Because 'wiretapping' is, you know, today it is different than wire tapping. It is just a good description. But 'wiretapping' was in quotes. What I'm talking about is surveillance."

So what's the verdict? All told, a pretty strong claim for defamation can be established by Obama against Trump, the man who often claimed while campaigning that libel laws needed to be eased to make the filing of suits easier. Obama could conceivably be entitled to punitive damages that are designed to hurt, to deter future wrongful behavior.

But of course, this all depends on the composition of the jury - and to many of the 46 percent who voted for Trump, this is all just noise.

Michael Smerconish can be heard 9 a.m. to noon on SiriusXM's POTUS Channel 124. He hosts "Smerconish" at 9 a.m. Saturdays on CNN.