Obama to give major immigration speech tonight. Why won't the major networks broadcast it?

At 8 PM on Thursday, President Obama plans to address the nation on immigration reform, one of the most politically explosive and highly contentious issues of his presidency. It's a major speech, one in which Obama is expected to announce sweeping immigration reform, including a plan to protect up to 5 million undocumented immigrants from deportation. The White House even promoted the speech in this Facebook video.

Yet, despite the speech's significance, the three major networks - ABC, NBC, and CBS - will not be airing it.

“In 2006, Bush gave a 17 minute speech that was televised by all three networks that was about deploying 6000 national guard troops to the border," a senior administration official told POLITICO. "Obama is making a 10 minute speech that will have a vastly greater impact on the issue. And none of the networks are doing it.”

Why aren't the major networks televising Obama's speech?

According to CNN Senior Media Correspondent Brian Stelter, administration officials put out feelers and determined that the networks would be reluctant to hand over air time, so decided not to formally request that they carry the President's address.

The networks that will be carrying the speech, however, provide insight. In addition to PBS, and cable news networks such as CNN, Fox News, and MSNBC, two Spanish-language networks, Univision and Telemundo, will broadcast the speech live. Univision is even delaying its broadcast of the Latin Grammys to accommodate Obama's address.

"It makes you think about who his audience really is, Stelter told CNN. "Maybe he's not trying to persuade the masses. Maybe he's trying to speak to a more niche audience, Republicans...for example, and trying to frame the debate on his own terms."

Some observers see the networks' decision as overtly political.

Politico has the the White House as "exasperated with the major broadcast networks...for skipping out on President Barack Obama’s Thursday primetime address," while Mediaite writes that "[T]he Obama administration...is curiously not trying to publicize it too hard."

When deciding whether to interrupt programming for a live presidential address, TV executives consider a number of factors. "One factor is whether the speech is "political" in nature," writes CNN's Stelter. "Some television executives said privately on Wednesday that they perceived Obama's planned address to be more overtly political than Bush's address on immigration in 2006."

In other words, the networks, mindful of their audiences, may have shied away from what they perceived as a divisive speech.

Of course, there may be a much simpler explanation for why the networks aren't carrying Obama's speech.

November is a sweeps month for the broadcast networks, a month-long evaluation period during which ratings are measured to determine advertising rates. And Thursday night is a big programming night for the major networks.

Obama will be competing against hit shows “Scandal,” “How to Get Away With Murder,” and the fall finale for "Grey’s Anatomy" on ABC; the “Big Bang Theory” on CBS and "The Biggest Loser" on NBC, while the intensely popular Latin Grammys are also scheduled to air on Univision.

The President will also be competing with the pre-game show for Thursday Night Football. The Kansas City Chiefs play the Oakland Raiders at 8:25 p.m.