Los Angeles Times: While reiterating his determination to run a positive campaign, Newt Gingrich took a veiled swipe at Mitt Romney over an attack ad now airing in Iowa, where voting in the Republican presidential contest is less than three weeks away. Gingrich, speaking to reporters in Iowa City, said that maintaining his lead in the polls ahead of the Jan. 3 caucuses is "going to be a challenge because you have everybody firing away simultaneously in a relatively small market."