After the Killian documents controversy, the onus is on the publisher to authenticate this type information before they publish it, not on the public to believe it until it is shown to be inauthentic. In that event, the Republican candidate was hurt by a forgery that then resulted in the resignation of Dan Rather, a very prominent news anchor.

In the impeachment case, that was not a case of the press digging up a document and making an accusation. It was the release of an accusation made to an inspector general. In and of itself, that is news. The fact that the white house was trying to prevent the release of the inspector general complaint to the Congress was also news. At that point, the veracity of the claim needs to be determined, and opinions clearly differed.

https://en.wikipedia.org/wiki/Killian_documents_controversy