'This Week' Transcript: Gov. Bobby Jindal and Rep. Jason Chaffetz

— -- ANNOUNCER: Starting right now on ABC This Week.

Stunning shakeup: Republicans in congress desperate to find a new leader as chaos erupts on Capitol Hill. Can someone finally bring the party together?

Plus, crunch time: Democrats preparing for their biggest moment yet, facing off in the make-or-break debate in just two days. With Sanders surging and Clinton struggling, who will come out on top?

And, is Biden finally jumping in? The clock ticking down on his 2016 decision. Why it could happen this week.

From ABC News, This Week with George Stephanopoulos begins now.

MARTHA RADDATZ, ABC HOST: And good morning. I'm Martha Raddatz.

So many developing stories as we come on the air. But we begin with the breaking news out of Turkey where twin bomb blasts have killed nearly 100 people at a peace rally. It's the deadliest terror attack in the country's modern history.

Turkey is a key U.S. ally in the war against ISIS. And ABC's Alex Marquardt is there with the latest.

Good morning, Alex.

ALEX MARQUARDT, ABC NEWS CORRESPONDENT: Good morning, Martha.

You can see here a large crowd that has gathered for a service for those who were killed in the attack yesterday. They are being called martyrs for freedom and democracy. The blast at the capital's main train station ripped through a crowd gathered for a peace rally. That the first blast caught on camera.

Afterwards, there was chaos and carnage everywhere, many fleeing, others trying to help the wounded as ambulances poured in.

Now Turkish officials are telling us today that the death toll has risen to almost 100 with hundreds more still in the hospital.

They think that suicide bombers carried out this attack, which is the worst terror attack in modern Turkish history. They say that ISIS or Kurdish militants are believed to be behind it, but so far there has been no claim of responsibility.

Now many in Turkey are blaming the government for breaking the truce with the Kurdish militant group the PKK. And with Turkey on the offensive about both ISIS and the PKK, many fear that this is a sign of more violence and bloodshed to come -- Martha.

RADDATZ: Thanks, Alex.

We're joined by former national counterterrorism center director Michael Leiter. And Michael, this, as you heard, the deadliest attack in Turkey's modern history. What effect will it have in the region?

MICHAEL LEITER, FRM. NATIONAL COUNTERTERRORISM CENTER DIRECTOR: I think a couple of effects, Martha. First of all, this really is Turkey's 9/11. This will be a massive effect on it politically. But it also -- this is all an outgrowth of Syria. Whether it's ISIS, whether it's an offshoot of the PKK, this all goes to Turkey's involvement in the region and the pressure which is coming out of ISIS because of the Kurds fighting.

ISIS and Assad, ISIS now being attacked by Turkey, it is showing really the cauldron that that region is. And it's making any stability for Turkey, an alignment between Turkey and Europe and NATO that much more difficult.

RADDATZ: And this week in Syria, we had the U.S. saying the training of Syrian rebels is not working. It's a failure. So now what?

LEITER: This is all very, very disappointing. I think all of us who have been arguing for a stronger action in Syria for a longer time have relied on air strikes in combination with an ability to train. And I think at its core, the problem with the training was not supporting people who were also going against Assad.