The people whose minds can be changed will feel they have no reason to watch them if the polls show a zombie landslide long enough.
There is a high level of interest across party lines in this first debate. People want to have their opinions validated. There is a percent of democrat voters, 2% - 5% who are persuadable. Romney’s team knows exactly who those voters are and will target them. If he gets even a portion of those and the majority of undecideds, he will win.