The two major party candidates for President appear in one Iowa city today — within four blocks of one another. Democratic presidential candidate John Kerry opens a roundtable discussion about the economy at 10 o’clock in Davenport, then shortly before noon President Bush is scheduled to headline a rally at a Davenport park nearby. Colin Van Ostren, a spokesman for the Kerry campaign, doubts the invitation-only crowd to the conversation with Kerry will wind up attending Bush’s rally. Van Ostren says the Secret Service has erected barriers that will likely keep the two crowds from mingling. No Davenport cop is being allowed to take time off today in order to help provide security, crowd control and traffic direction for the two events.