'This Week' Transcript: Donald Trump

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ANNOUNCER: Starting right now on ABC THIS WEEK. Trump, in it to win it.

DONALD TRUMP, REAL ESTATE DEVELOPER: Beautiful.

ANNOUNCER: The Donald solidifies his takeover of 2016. The massive rally, the surging poll numbers. This morning, the new sign Trump could be the leader for the long haul. He's here live

Plus, how Trump's opponents are fighting back. We'll ask Scott Walker. Can he out-trump Trump?

Biden running? His secret meeting this weekend. Does it mean he's about to jump in?

Plus, Hillary in trouble? The email firestorm growing. Why she's interrupting her vacation to get back on the trail.

And, American heroes. Breaking details about that fearless train tack down. U.S. servicemen risking their lives to stop a possible terrorist on the attack.

From ABC News, THIS WEEK with George Stephanopoulos begins now.

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GEORGE STEPHANOPOULOS, ABC HOST: Good morning. What some call a summer fling still going strong. Donald Trump drawing record crowds. He's going to join us live in a moment. But we begin with that brewing intrigue on the democratic side. Vice President Biden calling popular star Elizabeth Warren to Washington for a secret meeting on Saturday.

ABC's Jon Karl tracking all the latest from the White House. And Jon, this is the strongest sign yet that Biden is taking a serious look at this race.

JON KARL, ABC NEWS CORRESPONDENT: It sure is, George. This is a meeting between the two Democrats who could potentially pose the greatest threat to Hillary Clinton if either one of them decided to run.

Now Warren, of course, has emphatically ruled out running. Biden is seriously considering it. It's hard to imagine anything that would give him a bigger initial boost among base Democratic voters than support from Warren.

Warren, by the way, has been decided cool about Hillary Clinton's campaign. Just listen to this clip from a recent interview with WBZ in Boston.

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UNIDENTIFIED MALE: Was it a mistake for your party to anoint her as the nominee so early on?

SEN. ELIZABETH WARREN, (D) MASSACHUSETTS: Oh, I don't think anybody has been anointed.

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STEPHANOPOULO0S: So, Biden clearly sees an opening here with that lukewarm comment.

KARL: Absolutely. And especially in recent polls on the question of honesty and trustworthiness. Hillary Clinton is suffering largely as a result of this email controversy. Look at this recent Quinnipiac poll nationally, only 37 percent say that they trust Hillary Clinton, 57 percent say now.

When you look at Biden's numbers, they're almost exactly the reverse. A strong majority say that they find Biden honest and trustworthy.

STEPHANOPOULOS: The question is would he be willing to make that case if he did run.

What are they saying about timing, his advisers? I talked to one supporter this week who said it looks like Biden thinking he's about 60/40 to run. And they're feeling some pressure to make an announcement soon.

KARL: Yeah, no, what Biden himself is telling people, I am told, is that he has got quite a bit of time. He says the real deadline is that first Democratic debate, which is October 13.

But one very close Biden adviser told me yesterday that he that Biden has to do much quicker, has to make the decision much quicker. He starts, of course, way behind. He has no national organization, no fundraising. If he's going to run, he's got to get moving.

STEPHANOPOULOS: OK, Jon Karl, thanks very much.