Federal prosecutors are weighing bringing child-pornography charges against former congressman Anthony Weiner over sexually explicit exchanges he allegedly had with a 15-year-old girl, according to people familiar with the matter. In recent weeks, according to some of the people familiar with the matter, attorneys for Mr. Weiner have had discussions with federal prosecutors in Manhattan in hopes of dissuading them from bringing charges, or at least from bringing the most serious one: production of child pornography, which carries a 15-year mandatory minimum prison sentence upon conviction.