Massive Clinton landslide due to Wilson's pro-abortion position. This causes many conservatives to stay home/vote third party. Also, being warned about Pearl Harbor in advance didn't hurt FDR, and being warned about 9/11 in advance didn't hurt Bush Jr. Thus, I doubt being warned about Oklahoma City in advance would hurt Clinton, since he could always blame someone else. Finally, Bush Jr.'s inexperience causes many people to question Wilson's judgment in choosing him as VP and vote for Clinton (similar to McCain/Palin in 2008).