Transcript for Vice President Joe Biden Greeted by Big Applause as Hillary Clinton Loses Ground in Polls

behind you. To politics now, it O's your voice your vote. Joe Biden giving a speech thanking his supporters over the years. All this, as the Clinton camp could be in trouble, her lead shrinking in one key state. Dev yib with Dwyer is on the beat this morning and joining us from Washington. Reporter: That new trouble has trouble for Hillary Clinton. She's lost a third of her supporters in Iowa since may. Many consider Joe Biden. Overnight, vice president Joe Biden joining a jamboree of delegates. Biden didn't talk about a possible 2016, but his hugs and handsha handshakes, the door could be open for a Biden run. Hillary Clinton's lead in Iowa she rinking to its lowest ever. Just ahead of Bernie sanders. The socialist from Vermont now nipping at her heels. Even Biden, not in the race, draws 14% in iowa. On the republican side, Donald Trump continues to ride high in the latest poll, while Scott walker once the front-runner in Iowa seems to be disappearing. Leading big in Iowa, leading tremendously big in new Hampshire. Reporter: In Tennessee Saturday, trump drew a crowd of conservatives and protesters. Offering no apology for a sharp, new personal attack, this time on Hillary Clinton's most trusted adviser. She's married to a guy who's psychologically disturb. Reporter: Huma abedin is married to Anthony Weiner. The Clinton campaign swiftly condemning trump's statement as disgraceful. This, as the Clinton down plays those tightening results, they always expected this race to be close. So many talking about that poll this more. For more on this let's bring in Martha Raddatz who's hosting "This week" later this morning. What do his new poll Numbers say about the state of Hillary Clinton's campaign in Iowa? The campaign has to be worried, she's lost one-third of her support since may, but the campaign is putting the best spin on this, saying, we have always said that this would be a competitive primary, nothing is inevita inevitable. This morning, the pollster in Iowa who conducted the most recent poll said this feels like 2008 all over again. Let's turn to republicans, trump is up in the poll. Scott walker has to be another unhappy candidate taking a real tumble in the polls, the Des Moines register poll showing him now in a tie for third place. Number one in that poll in may. He's gone from 17% down to 8%. Donald Trump still has that significant lead. So much going on, okay, Martha, thanks so much. Watch "This week" here on ABC later this morning. Martha Raddatz will be speaking with Bernie sanders.

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