The polls make it obvious it's all name recognition. In which case Matthews's position in the primary looks very precarious indeed compared with his outperformance of the other Democrats in the general.
Out of curiosity, who do the Kos people like?
People on DailyKos don't particularly like Matthews. Some of that is for the same reasons that a lot of other people don't like him (he's kind of an ass, he never shuts up, he flip-flops constantly in whatever direction public opinion is moving). A lot of it was his cheerleading for Bush before he became unpopular. He also supported the war in Iraq. I doubt there's much of a consensus as to the other candidate's though. They also all pretty much uniformly dislike Specter and obviously want him defeated, despite Phil's arguments that he's a "liberal".