For example, from the Peter Strzok biography https://en.wikipedia.org/wiki/Peter_Strzok.
The revelation of the text messages led Republican congressmen and right wing media to start pushing conspiracy theories to the effect that Strzok was involved in a secret plot an undermine the Trump presidency[13][14][15][16]
This contains information where the writer is adding his own opinions about who is right wing. That's a subjective opinion. The specification that the Congressmen were Republican is irrelevant, why not say, the congressmen were from Missouri or Ohio? It doesn't matter where they are from from what party they are members of. Any additional information added which is not relevant to the facts at hand is an attempt to bias the data.
These are both example of "loaded language" https://en.wikipedia.org/wiki/Loaded_language
Cleaned up, the sentence should have read something like this:
The revelation of the text messages led some congressmen and media sources to suggest that Strzok was involved in a plot an undermine the Trump presidency[13][14][15][16] and they used the text messages as part of a campaign to discredit Mueller's investigation.