John Fund offers this Opinion Journal column. John says: “Just before the 2004 election, the influential blog DailyKos.com warned of a ‘nationwide’ wave of voter fraud against John Kerry. After the election, liberal blogger Josh Marshall urged Mr. Kerry not to concede because the election had been ‘too marred with voter suppression, dirty tricks and other unspeakable antics not to press every last possibility’ of changing the outcome.”
Josh’s quote of course does not mention “voter fraud,” and I’d be surprised if Markos (or anyone else writing directly on the site, as opposed to in a diary) claimed “voter fraud” either. Perhaps John can send me the links so we can see if any respectable liberal bloggers made this claim before the 2004 election. My guess is no.

UPDATE: In an email, John Fund points me to this post by Kos on Oct. 31, 2004. Though the post indeed has the title “Voter Fraud and Disenfranchisment,” it has nothing to do with “voter fraud” as Fund means the term—voters improperly voting as someone else or voting twice—and everything to do with vote suppression.
UPDATE 2: Bob Bauer comments.