All I've seen on the little TV I watch is Smith ads since before the primary. I could see the race being somewhat close now, until Casey starts running more ads.
As a fun fact, it was the same way for the 2006 race. Santorum ran ad after ad attacking Casey for a good three months before I saw Casey's first ad. I don't know why he waits so long. Or maybe I'm just really unlucky and don't ever see any of his.
Casey might have underestimated Smith and had not planned to run any TV. Smith is running some fairly good attack ads in Phila. I can see him closing, but not winning. Also, Smith was running against three people in the primary and that is why you saw so many ads. He was
not the endorsed GOP candidate and
not the Tea Party candidate, IIRC.