In the sprawling Clinton body politic, Shareblue is the finger that wags at the mainstream news media (“R.I.P. Political Journalism (1440-2016)”) or pokes at individual reporters. It is a minor appendage, but in an increasingly close race for the presidency, it plays its part.

And it is already warming up for the biggest event of the general election so far: the first debate, on Monday night. It has already published a piece calling on moderators to fact-check Mr. Trump on the spot, and will continue through debate night, whipping up support online with the hashtag #DemandFairDebates.

Shareblue is owned by David Brock, the onetime Clinton critic who remade himself into a Clinton supporter and architect of a conglomerate of organizations designed, he said, to be the liberal answer to the conservative messaging of Fox News.

The Brock network includes his Media Matters for America watchdog website; two pro-Clinton “super PACs,” the opposition research outfit American Bridge and the pro-Clinton fact-checking and reporter-spamming operation Correct the Record; and Shareblue, which filled the need, Mr. Brock said, for a progressive outlet that spoke directly to the grass roots and which “was avidly and unabashedly pro-Hillary.”

Shareblue’s bread-and-butter content is exposing what it considers to be news coverage stacked against Mrs. Clinton. Mr. Daou was particularly excited about a project seeking to show that Mrs. Clinton’s email travails had been in the news every day since the story originally broke in March 2015.

Often, their editorial direction seems in sync with the Clinton campaign, which has instructed its surrogates to blame news coverage for negative press. “Are they going to hold Hillary to a different standard again?” read one recent “talking points” memo sent by the campaign to its surrogates.

That approach became clear this month. On Sept. 1, The Washington Post broke a story about the Donald J. Trump Foundation being fined for improperly donating $25,000 to Pam Bondi, the attorney general of Florida, around the time that her office was deciding whether to investigate fraud allegations against Trump University.