Transcript for Bernie Sanders, Hillary Clinton Share Stage in Iowa

We'll switch gears to the race for the white house. Your choice, your vote and the unexpected twist for Hillary Clinton. Many people thought her run for the democratic nomination would be a cakewalk but there she was in Iowa overnight sharing the stage for the first time with Bernie sanders, the socialist senator from Vermont who is generating surprisingly robust crowds and excitement and Devin Dwyer is on the story from the white house. Reporter: Things starting to get interesting for democrats. Bernie sanders, Hillary Clinton, the other democratic candidates, as you said, on the stage together in Iowa side by side for the first time. They didn't go after each other by name but it's clear this nomination race is heating up. For democrats, it's finally a face-off. This country belongs to all of us. We are ready to win this election. Reporter: Overnight Hillary Clinton sharing the stage in Iowa for the first time with Bernie sanders, the socialist from Vermont who's been drawing huge crowds. We need a mass movement from coast to coast. I'm running for you. Reporter: Clinton the front runner meeting real competition in Iowa for the first time. Standing shoulder to shoulder with former governors martin O'Malley. Lincoln cave if I and former senator Jim Webb. Die-hard democrats are excited to size up their options. Hillary popular but 70% of democrats in the latest ap poll see her favorably, down 11 points since April. Thank you so much, Iowa. Reporter: The Clinton campaign announcing Friday it's buying its first TV ad time. Every day Americans need a champion. Reporter: Spending more than $7 million in the early primary states including nearly $4 million in Iowa. Bernie sanders hasn't announced a single major ad buy. There is nothing we cannot accomplish. Reporter: Today republicans are attending another Iowa cattle call too. 10 of the 15 candidates in the gop race con virgining on a summit with religious conservatives. Donald Trump who is on the cover of "The new Yorker" making a belly flop splash is near the front of the pack saying he expects to win Iowa. Now, Wisconsin governor Scott walker and former Florida governor Jeb bush also near the front of the pack there in Iowa. Almost all the 2016 candidates will be swarming the state this weekend. Those critical Iowa caucuses just about six months away, Dan and Paula. Full employment act for political reporters across the country. It's going to be a great race. Devin, thank you.

This transcript has been automatically generated and may not be 100% accurate.