And it still wasn't enough. To paraphrase: It Wasn't Close; They Couldn't Cheat.
Kerry knew this, so he conceded. Had he challenged, it would have been investigated. He still would have lost, and all the evidence of the Democrats electoral shenanigans would have come out. The Democrat Party would have been destroyed forever (with certain important members spending a considerable time in jail).
In other words, the Democrats realized their best campaign workers won't be able to help Hillary in four years if they are still serving a five year sentence for vote fraud.
They thought they had it in the bag, like FL in 2000 but somehow there cheating didn't work. In 2000 it was due to stupid and illiterate cheaters, in 2004 we expected it and the right wing vote overwhelmed the cheaters, they did not expect the turnout.
I would say that at least 10% 0f sKerry's votes should be tossed.