'This Week' Transcript: Dr. Ben Carson and Samantha Power

— -- THIS IS A RUSH TRANSCRIPT

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ANNOUNCER: Starting right now on ABC's THIS WEEK, two stunning shake-ups. The House speaker abruptly resigns...

(singing)

ANNOUNCER: -- rocking the GOP.

And a brand new poll showing Ben Carson now in a dead heat with Donald Trump.

Are outsiders now in charge?

Dr. Carson is here.

And Pope Francis in America -- record crowds going wild in Philadelphia, with the pontiff's powerful message of hope -- what he's about to reveal on his final stop in the US.

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

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MARTHA RADDATZ, ABC NEWS HOST: Good morning.

I'm Martha Raddatz.

As we come on the air this morning, we want to get right to two stunning developments in the 2016 race.

First, to the Republicans. A new national NBC News/"Wall Street Journal" poll revealing Donald Trump's once formidable lead now gone. Dr. Ben Carson continuing to surge, now in a dead heat with Trump. You see it right there.

Trump 21 percent, Carson at 20. Another outsider, Carly Fiorina, surging, as well, now tied with Marco Rubio for third.

And on the Democratic side, the party establishment not faring much better. Bernie Sanders now within just 7 points of frontrunner Hillary Clinton.

Dr. Carson joins us in just a moment.

First, the 2016 race is already feeling shockwaves from the other big political news, House Speaker John Boehner's bombshell resignation. The fallout for Republicans growing.

ABC's Jon Karl has the latest.

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REP. NANCY PELOSI (D-CA), HOUSE MINORITY LEADER: God bless you, Speaker Boehner.

JONATHAN KARL, ABC NEWS CORRESPONDENT (voice-over): It was the Tea Party wave in 2010 that made John Boehner speaker of the House. He had spoken their language in the fight over ObamaCare.

REP. JOHN BOEHNER (R-OH), SPEAKER OF THE HOUSE: Hell no, you can't.

KARL: Hell no soon became the de facto motto of the House conservatives, who often made Boehner's life as speaker a political hell and ultimately did him in. He faced an ugly fight just to keep his job.

BOEHNER: And this turmoil that's been churning now for a couple of months is not good for the members and it's not good for the institution.

UNIDENTIFIED MALE: Speaker Boehner announced that he will be resigning.

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KARL: At a forum of conservative voters in Washington Friday, Boehner's resignation got a standing ovation, the same anti-establishment forces that are shaking up Congress have also up-ended the race for the White House. The surest way for Republicans running for president to gain points is by slamming Republicans running Congress.

DONALD TRUMP (R), PRESIDENTIAL CANDIDATE: They get elected. They're full of vim and vigor. They're going to change things. They come down to these magnificent vaulted ceilings that you see all over Washington and what happens?

They become different people.

KARL: Ultimately, John Boehner was the top leader in a Congress unwilling to be led.

UNIDENTIFIED MALE: I'm not surprised the pope inspired Boehner to resign. It must have been difficult for the Republican leader to sit there and watch someone whose followers actually listen to him.

KARL: The visit of Pope Francis was the emotional high point of Boehner's tenure. The former altar boy had been trying to get a pope to address Congress for 20 years.

BOEHNER: I have the high privilege and the distinct honor of presenting to you, Pope Francis of the Holy See.

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KARL: It was also the moment that prompted his big decision.