'This Week' Transcript: Sen. Marco Rubio and Sen. Bernie Sanders

— -- THIS IS A RUSH TRANSCRIPT FOR 'THIS WEEK' ON JANUARY 10, 2016 and it will be updated.

ANNOUNCER: Starting right now on ABC's THIS WEEK, just three weeks to the first votes, Donald Trump still on top for the GOP.

But can he stop Ted Cruz in Iowa?

(BEGIN VIDEO CLIP)

SEN. TED CRUZ (R-TX), PRESIDENTIAL CANDIDATE: I think my record is stronger than his.

(END VIDEO CLIP)

ANNOUNCER: And is this man the Republican establishment's last best hope?

We're one-on-one with Marco Rubio in an ABC News exclusive.

Plus, Hillary's surprise battle with Bernie, as Sanders surges in the early states. The gloves are off.

(BEGIN VIDEO CLIP)

SEN. BERNIE SANDERS (I-VT), DEMOCRATIC PRESIDENTIAL CANDIDATE: We are the campaign that's going to win this election.

(END VIDEO CLIP)

ANNOUNCER: Senator Sanders is with us live.

And an exclusive inside look at what Iowa voters think about both sides of the race.

And a brand new forecast on Iowa and New Hampshire from the man who got them all right in 2012.

From ABC News, THIS WEEK WITH GEORGE STEPHANOPOULOS begins now.

GEORGE STEPHANOPOULOS, ABC HOST: Good morning.

It has already been one of the most volatile and unpredictable primary campaigns ever. And now, the first votes in the race for president are coming fast.

With just three weeks until Iowa, we start out with an exclusive look at how Iowa voters are thinking about this race.

Here's Jon Karl.

(BEGIN VIDEOTAPE)

JONATHAN KARL, ABC NEWS CORRESPONDENT: With just 22 days until voting in Iowa, this weekend, frontrunners Donald Trump and Ted Cruz barnstormed the Hawkeye State. While Trump still holds his national lead, Cruz is on top in this year's first poll of Iowa voters. And now Cruz is questioning whether Trump has what it takes to win in Iowa.

CRUZ: It's very time intensive. It's labor intensive. You don't do it sitting back in the easy chair. You don't do it from a TV studio in Manhattan.

KARL: An issue raised at a focus group of likely Republican caucus-goers in Iowa conducted by focus group guru, Frank Luntz, and Google. ABC News got an exclusive first look.

UNIDENTIFIED MALE: How many of you say Trump is going to win?

Raise your hands.

Oh, he won't be happy with that. Only two of you.

How many of you say Ted Cruz is going to win?

If Trump is the nominee, is there anyone in this room who would not vote for him?

Wow!

UNIDENTIFIED FEMALE: I do not believe that Trump would put a good face on the Republican Party as president.

UNIDENTIFIED MALE: So you'd be prepared to see Hillary Clinton in the White House?

UNIDENTIFIED FEMALE: Unfortunately.

KARL: But others find a lot to like about him.

UNIDENTIFIED MALE: The man knows how to negotiate. He knows how to find the right people.

KARL: Trump's first television ad, promoting his Muslim ban, generated the expected buzz.

UNIDENTIFIED MALE: It's spot-on. It's -- the things he talks about in that ad is what's affecting America right now, illegal immigration and ISIS.

UNIDENTIFIED MALE: But does he do it in a way that's constructive?

UNIDENTIFIED FEMALE: No.

UNIDENTIFIED MALE: No.

UNIDENTIFIED FEMALE: No.

UNIDENTIFIED MALE: Absolutely not.

UNIDENTIFIED FEMALE: (INAUDIBLE).

KARL: With this group, Trump's questions about whether Cruz was born in Canada to an American mother, is eligible to be president, actually appeared to backfire.

UNIDENTIFIED MALE: It exposes Trump as not serious. Just a few months ago, he said his strongest lawyers said it's a settled issue and Cruz is eligible.