WASHINGTON (CBS News) - This week on "Face the Nation," we released new Battleground Tracker Polls showing businessman Donald Trump and former neurosurgeon Dr. Ben Carson tied neck and neck in Iowa. We spoke with the Republican front-runner, Donald Trump, about the new poll as well as his recent attacks on his Republican rival, Dr. Carson. We also spoke with fellow Republican candidate and governor of New Jersey, Chris Christie, where he shared his thoughts on Hillary Clinton, the Black Lives Matter Movement and a wide array of other topics.
At the top of Sunday's broadcast Republican front- runner Donald Trump called in to discuss our recent poll numbers with our host, John Dickerson. Although Trump maintains a significant lead in every other battleground state so far, our new polls show him and Dr. Carson tied at 27% in Iowa.
"Well, I don't understand Iowa," Trump told Dickerson, "because, frankly, I just left. And we had tremendous crowds and tremendous enthusiasm. And, frankly, even to be tied, I'm a little surprised."
With Carson rising in the polls, Trump spent last week attacking his Republican rival. His most notable comments were the ones made at an event in Florida, where Trump raised questions about Carson's religion. At the event Trump said, "I mean, Seventh Day Adventist, I don't know about. I just don't know about."
When Dickerson asked the front-runner what he meant by those remarks, Trump clarified them by saying, "That wasn't meant to be an insult, obviously. It's just that I don't know about it."
Later in the show, fellow Republican presidential candidate and governor of New Jersey, Chris Christie, joined Dickerson in the studio and discussed the Benghazi Hearings and former Secretary of State Hillary Clinton. Christie attacked the Democratic presidential front- runner, Clinton, by calling her "unaccountable."
"I think what the American people dislike most about Hillary Clinton is that she refuses to be held accountable." The governor said.
Christie also had strong criticisms of Barack Obama and the Black Lives Matter Movement. Christie explained that the president "doesn't back up the police," and that he "justifies Black Lives Matter." When Dickerson pressed Christie on whether or not the movement should be justified, the New Jersey governor responded by saying, "I don't believe that that movement should be justified when they're calling for the murder of police officers, no."
Finally, CBS News released a new Battleground Tracker Polls for both the Republican and Democratic race. CBS News Election's Director Anthony Salvanto joined us on Sunday to give his takeaways on the newly released polls. On the Republican side, Donald Trump maintains a significant lead in all of the battleground states except for Iowa where he is tied with Dr. Ben Carson.
The Democratic side shows Hillary Clinton moving up in states like Iowa, and growing a firm lead in South Carolina where she is up big at 68% followed by Vermont Senator, Bernie Sanders at 25%. Sanders, however, maintains his lead in New Hampshire where he is up 54% followed by Clinton at 39%.
Salvanto attributed Clinton's resurgence in the polls to Vice President Joe Biden's decision not run as well as key factors like her experience and electability that were showcased at the CNN Democratic Debate earlier this month.
For more information on the new CBS polls click here.