However, in 2008 there was a lot of anxiety here about the election's being rigged in 11/08 and in '04 the consensus for a reasonable portion of DU was that the elections had been rigged.

Even in the shadows this past summer and spring there was a sort of "the media are rigging the elections" mood. It's a kludge to explain why your side isn't a majority. When (D) weren't the winners, they were obviously still clearly the majority so the elections had to be rigged. When Obama won in '08 the evidence was clear that the elections were fair.

The word gets way overused.

There's bias, which can come in several forms including the kind that is often blamed on "the media".
There is the kind where voter registration and voter precincts are positioned to bias participation.
There is the "voter intimidation" which is part of this where various groups try to coerce people through threats.
There's the kind where various forms of ballots such as absentee are abused by people "helping" in filling them out.
Then there is the kind where folks in power fill out ballots enmass for a particular candidate. This kind by the by these days is fairly rare, especially in a national election. Just too many folks watching these days. And the volume required to affect a state wide election can be huge.

Trump is predominately talking about media bias, when he bothers to be specific at all.

DU usually makes reference to the second kind, precinct bias so to speak, which includes things like voter ID and poll hours. Although there are often concerns about the last kind, especially with all of the electronics being used today.

The problem is much of the tea party types presume there is massive amounts of the last kind, and it just isn't so.