![PBS NewsHour - Segments show](https://d3dthqtvwic6y7.cloudfront.net/podcast-covers/000/082/426/small/pbs-newshour-segments.png)
Summary: As the Democratic presidential candidates angled for attention in Iowa, new polling suggested a shifting political reality. Sen. Elizabeth Warren has stepped into first place in that state, over former Vice President Joe Biden and Sen. Bernie Sanders. For candidates who didn't make the top slots, the new numbers are making them rethink their strategies. Lisa Desjardins reports.