It began with a phone call, became a tweet, and passed to a website and an online magazine. From there, during one of the year's slowest news weeks, it blazed like a brushfire into blogs, social media, talk radio - and cable TV, where a single comment threw gasoline on the blaze.

The topic: a call from President Obama to Eagles owner Jeffrey Lurie that touched on star quarterback Michael Vick - who, before joining the Eagles in August 2009, served 19 months on a felony charge stemming from his involvement in a dogfighting ring in which dogs were tortured and killed.

It's a study in how media trickles become tidal waves, and it started, as so many news stories now do, with a tweet.

Peter King, a reporter for Sports Illustrated and NBC Sports, posted on Monday night: "Yes, Obama called Eagles owner Jeffrey Lurie to praise the Eagles for giving Vick a chance. Said too many prisoners never get fair 2d chance."

It's unclear exactly when Obama called (Lurie has not said, and neither the Eagles nor Vick had further comments as of Wednesday), or what his main subject was. King's tweet suggests it was Vick-related praise; White House spokesman Bill Burton, seeking to plug the dike, said talk also concerned plans for windmills, solar panels, and other green-energy measures at Lincoln Financial Field.

Burton also said Obama "of course condemns the crimes that Michael Vick was convicted of, but, as he's said previously, he does think that individuals who have paid for their crimes should have an opportunity to contribute to society again."

Largely ignoring Burton's spin, blogs throughout the land picked up the story, with edge. The Source.com blared: OBAMA GIVES VICK AN EARLY PARDON. DeathBy1000PaperCuts.com ran with: OBAMA CALL SUPPORTING MICHAEL VICK LEAVES PRESIDENT IN DOGHOUSE. And the Washington Post mainstreamed it on the front page Tuesday: ON VICK, OBAMA AGAIN STEPS OUTSIDE LINES.

Old questions reignited: Was Vick's fine play this season a sign of "redemption"? Had his punishment been equal to the crime? Did sports have anything to do with such moral questions in the first place? Had the president overstepped or not?

The affair became a leading "trending topic" on Twitter, as tens of thousands of tweeters bandied it back and forth. Sports-talk radio entertained callers with passion on all sides. According to one source at 97.5 The Fanatic who asked not to be identified, "Just the name Michael Vick makes the phone ring like I've never seen. People either love him or hate him."

And it was rare steak for 24/7 cable TV news and opinion. The world was about to see an example of what Matthew Kerbel, professor of political science at Villanova, calls "a growing convergence between TV and the Internet."

In a news-dead week, news channels embraced what had begun as a Web-based story. On CNN, White House correspondent Suzanne Malveaux asked former sports commentator Pat O'Brien: "Is this what it looks like to seek public forgiveness, and to get public forgiveness?"

O'Brien replied, "I don't know what people want [Vick] to do. He apologized." When asked whether Obama should have gotten involved, O'Brien replied, "I think he should get involved in these things. There are some presidents who probably would not have known . . . who Michael Vick was, or Kanye West. . . . Second chances are what America is all about."

Fox News spent much of Tuesday on Vick/Obama, and on Tuesday night, the big blast came. Commentator Tucker Carlson, filling in for Sean Hannity, said: "I'm a Christian, I've made mistakes myself, I believe fervently in second chances. But Michael Vick killed dogs, and he did in a heartless and cruel way. I think, personally, he should have been executed for that."

Carlson's words - or word, executed - ignited yet another firestorm. Blogs and online journals championed or attacked his words. Glenn Davis of blog site Mediaite.com wrote that "to hear a pundit openly opine that a prominent person should have received the death penalty - and being completely sincere in doing it - is not something you'll see too often."

As of 6 p.m. Wednesday, Tucker Carlson was the fourth leading Twitter topic.

Ed Morrisey of HotAir.com did something a lot of bloggers don't: He got on the phone. He said Carlson told him: "I love dogs - we have three - and I think what Vick did was horrifying and shockingly cruel. Executed? I don't know. I do know that 19 months is a joke. People get more than that for tax evasion. He certainly shouldn't be back in the NFL with Obama rooting for him. What the president said is disgusting."

The story now has viralized into sports (Vick; his fall and rise; crime and forgiveness) and politics (Should Obama have weighed in? Will it help? Hurt?), with spins from right (Obama is inappropriate, soft on crime, disappointing ) and left (Carlson's irresponsible, extreme, should be fired).

As Chris Good, staff editor of Atlantic.com, observes, "A lot of information on the Internet quickly occupies niche spaces, for specialized audiences, which use it for their own purposes." In the Vick/Obama case, two such niche audiences are the prison-rights community and animal-rights advocates.

In the online Daily Beast on Tuesday, ex-convict Mansfield Frazier wrote that the president's call created "an opening for a national discussion on opportunities for former prisoners." Prison-advocacy blogs see Vick/Obama as a lesson in the need for society to accept reentry felons.

As for animal-rights advocates, Bill Smith, founder of Main Line Animal Rescue in Chester Springs, says he's "tired of discussing Michael Vick" and suggests that "instead of calling the owners of the club," Obama should have called animal shelters and found out about the dogs. "A lot of rescues and shelters in the United States remember his promise two years ago to adopt a shelter dog," Smith says. "Had he done that, people wouldn't be judging him as severely as they are now."

John Polis is senior manager of public relations for Best Friends, a Utah sanctuary for abused animals. Twenty-two of the dogs confiscated in Vick's arrest were taken in there, and Polis says five to six are either adopted or about to be. "When I went to Vick's sentencing, all the story was about 'Michael and what's going to happen to him,' " he said by phone. "And today, the story's still about him. The dogs are the forgotten ones."

Sports Illustrated's King probably never thought his tweet would become a story this big. In a later tweet, he wrote that "this story has longer legs than Giselle" - meaning, possibly, Giselle Bündschen, wife of New England Patriots quarterback Tom Brady, supposedly Vick's rival in the 2010 MVP stakes.

To have legs in this media world, as King surely knows, all a story needs are mouths, ears, and eyeballs. The Vick/Obama saga is attracting a whole lot of all three.

Contact staff writer John Timpane at 215-854-4406, jt@phillynews.com or twitter.com/jtimpane.