Noted: To mobilize younger voters who supported him in 2008, Mr. Obama will hold four big campaign-style rallies, the first Sept. 28 at the University of Wisconsin in Madison, with satellite transmission to campuses in other states. The later rallies will be in Ohio, Philadelphia and Las Vegas. He also will send e-mail and record robocalls to spur voters, and conduct a national ?town hall? Webcast in October.