NEW YORK — Conservative legal advocates are recruiting pastors nationwide to defy an IRS ban on preaching about politicians, in a challenge they hope will abolish the restriction. The Alliance Defense Fund, based in Scottsdale, Ariz., will ask the clergy to deliver a sermon about specific candidates Sept. 28. If the action triggers an IRS investigation, the legal group will sue to overturn the federal rules, which were enacted in 1954. Under the IRS code, churches can distribute voter guides, run voter registration drives, hold forums on public policy and invite politicians to speak at their congregations. However, they cannot...