The pool reporter files that report to every news organization in the pool. TPM is part of the DC pool but not the traveling pool.
This whole system is run by the White House Correspondents Association which, yes, is the same group that puts on the rather ridiculous but entertaining White House Correspondents Association Dinner. Now, the WHCA spends a lot of time obsessing about what I would call access formalities - often to the detriment of more substantive and significant journalistic issues. In an of itself this protective pool issue is a pretty marginal one, certainly while Trump is the president-elect. But it's not in and of itself. Trump has been notoriously, historically opaque through the campaign. He's the first candidate in decades never to release his tax returns. He spent much of the campaign not just vilifying the press but actually inciting supporters against his traveling press. Any effort to turn back the unofficial norms that allow news organizations to scrutinize and inform the public about the president should be greeted with serious and grave concern.
Things like clampdowns on FOIA, exclusion of meddlesome, non-friendly reporters from the White House briefing room and a host of other things would be much more ominous. But this happened on the new President-Elect's second day with the title. That's a bad sign.
Which gets me to the larger point about the mainstream media. Let me start by defining terms. We are talking about large news organizations which at least purport to be apolitical in their editorial outlook and are owned and controlled by large corporations. People have lots of different definitions of the "MSM". But I think this is the most valuable one for present purposes.
Two things to keep in mind: all of these organizations have business models which are based on appealing to people across the political spectrum. So for instance, CNN cannot afford in business terms to get too out of sync with Trump and his supporters. (This is one of the big points about the campaign. Trump harped continuously on CNN but it was in fact one of his most accommodating news organizations. It even hired a group of bespoke supporters as pundits for the duration of the campaign. He harped on them because he saw them correctly as the most vulnerable.) Second and just as important, every big media organization and especially every big diversified corporation that owns a media organization have lots and lots of business before the federal government all the time. Even for broadcast TV networks alone there are regulations about how many local stations they can own. Telecoms like Comcast, which owns NBC, have a long, long list of business before the government.
What it all comes down to is that the corporations that own these big branches of the news media are vulnerable to cajoling and punishment by an unscrupulous government with authoritarian tendencies. That is a big, big deal under present circumstances.
What's more, reporters require access. Some of this is simply what reporters and news organizations think they need as opposed to what they do need. But reporters do require some level of access to do their job. Yet they have no way to compel it. There is a very slippery slope to compromising yourself as you try to gain the kind of access - simply getting basic questions answered - you need to do your job.
Looking back on the previous campaign, consider that virtually all we knew about Hillary Clinton, her finances, the Clinton Foundation and everything else (aside from the stolen emails which added a great deal more) were the product of voluntary disclosure. Trump didn't disclose anything. It makes all the difference in the world. Reporters could grouse a bit. But he didn't care. All of her emails were released by a State Department run by a president of her own party which acted in compliance with established norms and court orders. All of that stuff can simply change.
There is of course tension between every administration and the press over access and transparency. But again, Trump isn't any soon-to-be-president. Just last night he was on twitter accusing the "media" of 'inciting' protests against him. This is not normal. Big news organizations will be under a great deal of pressure for all the reasons above to normalize Trump's behavior. Small, independent organizations will be better able to resist that urge in some ways. But they are also more legally vulnerable and most importantly in the nature of things they have smaller audiences.
And let me clear about a final point. I'm not saying the MSM is feckless or will be cowed. I know a lot of these people. A lot of them are worse than you can imagine; a lot are far braver, more principled and more honorable than you probably realize. My point is that they and more so the institutions they work for are highly vulnerable to pressure by someone who simply ignores the existing rules.