I was watching "Outfoxed" and some guy said something completely true, IMHO. He said that FOX's and then the other networks decisions to call Florida for Bush at 2 AM even though you really couldn't tell from the data, led to a perception throughout the legal battle that Bush was the current winner and Gore was trying to knock him off. That perception may have hurt Gore more than any legal mistake or something of the sort.
The call at 2 AM was when no more votes could be cast, however when Florida was prematurely and erroneously called for Gore earlier that night thousands of people in Florida and beyond still could. This of course caused many Bush supporters in the Panhandle not to vote thinking that their man had already lost. Also you say that the perception that Bush was the current winner hurt Gore. The fact is that from that moment on Bush WAS the current winner. He was the current winner when the initial vote was tallied and he lead by 1,784 votes. He was the current winner after the State mandated recount. He was the current winner after Volusia county turned up a net of 98 Gore votes. He was the current winner after the overseas votes were tallied (with a 930 vote margin). He was the current winner when Broward and Palm Beach turned in their (possibly unconstitutional) recounts. He was the the current winner when Katherine Harris finally certified him as winner (by 537 votes). He was current winner when the case appeared before the Supreme court. The fact is throughout the legal battle Gore WAS trying to knock him off. The mistake that hurt Gore was how he acted like a "sore loserman" after it was clear Bush had won.