As President Obama convenes the first direct Middle East peace talks in 20 months, the question many observers here and in the region are asking is what, if anything, makes this round any more hopeful than the last.One reason for optimism may be the shared regional fear of Iran, which has only grown since talks broke off between Israelis and Palestinians in December 2008.Obama began a series of bilateral meetings Wednesday morning with the four leaders involved in the talks. Each has his own interest in seeing them succeed, but Iran's threat is a common concern to all of them.