A RUNOFF election next month to determine if Chicago Mayor Rahm Emanuel gets a second term appears to be close. His opponent, Jesus “Chuy” Garcia, is not as well known and has far less campaign money, but recent polls show him within single digits of Mr. Emanuel. Democratic Party purists and special interest groups have reached the startling conclusion that the able and decidedly liberal incumbent is not liberal enough, and they are intent on punishing him for not toeing their line.