No, McCain got a large number of votes from union goons and Bush haters whole sole purpose in voting that day was to vote for McCain to make Bush look bad. Had McCain gotten the GOP nomination, 99 out of 100 of them would have voted for Gore in November.
A late April poll of registered voters by the Chicago Tribune showed incumbent Durbin leading Durking 49-33%, with a MOE of 4%. Durkin had 73% name recognition, and the accompanying analysis of the poll said the results suggested Durkin with a "K" could tighten the race if he could raise funds and his profile. McCain could definitely help him do that.