How many reporters does it take to cover liberals?

It's a trick question. First, you have to ask, as Byron York does with Sherlockian insight, why there are reporters "covering" conservatives, as Dave Weigel was supposed to do, in the first place? Answer: because conservatives are a puzzling, alien phenomenon to MSM editors/producers. Here's the money quote:

In the past several years, newspapers have assigned reporters to specifically cover conservatives, but they haven't done the same thing for liberals. It started in January 2004, when the New York times chose David Kirkpatrick to cover the conservative movement. The goal, as Times editor Bill Keller told then-ombudsman Byron Calame in 2006, was to identify "the [conservative] thinkers and the grass roots they organize" and explore "how the conservative movement works to be heard in Washington."

"We wanted to understand them," Keller said of conservatives.

So, the answer to the question about the number of reporters needed to cover liberals is zero, since there's clearly no lack of understanding of that kind of politics within the MSM. But if the question is, how many reporters do cover liberals, explicitly or tacitly, the answer must be just about all of them.