President Barack Obama on Wednesday released his long-form birth certificate in an effort to end the "birther" debate over whether he was born in the United States.

The debate, which has lingered around Obama since he campaigned for president in 2008, has been a favorite topic of some conservative talk radio and bloggers. But Brian Stelter of the New York Times says other media kept the debate alive, as well.

In waves of media coverage - the vast majority of it critical of the so-called "birther" position - reporters tried to debunk those theories. But opinion polls found that doubts among Americans about his citizenship grew over time, as if the very fact of the debate caused the issue to fester in more minds.

While the debate simmered over the past two years, it came to a boil in recent weeks as celebrity mogul Donald Trump expressed his doubts about Obama's birthplace. Trump claimed to have his own team of investigators in Hawaii trying to find proof of Obama's birth and challenged the president to release his long-form certificate. 

As Trump continued to push his challenge to Obama, more Americans expressed their own doubts. A recent New York Times survey found that nearly 25 percent of Americans believed Obama was born in another country; 45 percent of Republicans said they believed that. The poll numbers caused some news agencies to act, Stelter writes.

Only after Trump spoke out did it become a major topic for the news media. Fox News Channel commentators, who had rarely invoked the issue, started bringing it up, as did their guests; Sean Hannity, Fox's 9 p.m. host, asked repeatedly in March, "Why can't they just release the birth certificate?"

Indexing of last week's news coverage by the Project for Excellence in Journalism found that of the three main cable news channels, MSNBC hosts spent substantially more time talking about the citizenship issue than those on CNN or Fox News.