Judy Woodruff:

Jumping in just a month ago, Bloomberg has shot up in recent polls, after spending millions of his personal fortune on campaign ads.

The others in the race spent a lot of time in Iowa, hoping to sway voters who remain largely undecided, with just six weeks before the state's first-in-the-nation caucuses.

Former Vice President Joe Biden traveled across the Hawkeye State, knocking on doors and talking to voters at a local Christmas tree farm. Speaking at a town hall, he focused on the importance of unity.