‘Kenneth L. Wainstein, the White House adviser on homeland security and counterterrorism, recently visited Denver and St. Paul, a trip that reflected the administration’s interest in the conventions. “In the post-9/11 world, you have to prepare and plan for all contingencies,” Mr. Wainstein said. “That means preparing for everything from a minor disruption and an unruly individual to a broader terrorist event. We need to plan for everything no matter what the threat level is on any particular day.”’