Bush had mentioned his plan before he gave the official announcement.
The price drop was in direct response to Bush just mentioning that he was in favor of drilling.
June 18th - Bush announces plan to push Congress to eliminate the offshore ban.
June 30th - New High for Oil prices of 137.
July 3rd Oil prices close at record price at 143.95
July 14th Oil climbs back up to 142.43 after dropping to 133.91 the week before.
There was no "direct response" to Bush mentioning he was in favor of drilling. Oil went UP for the 2 weeks after he mentioned it and stayed up for almost a month.