Joe Biden slumps in Iowa poll as Pete Buttigieg surges

South Bend Mayor Pete Buttigieg made gains in Iowa, as former Vice President Joe Biden slipped in a New York Times/Siena College poll of voters likely to attend the state's caucuses. Sen. Elizabeth Warren leads the deadlocked pack, with Sen. Bernie Sanders coming in next.

Why it matters: "Buttigieg is aiming to peel away support from Mr. Biden by offering himself as the viable moderate alternative" to Warren and Sanders, the New York Times wrote last week. That effort appears to be working.