those are the things i would be looking at to show evidence of obstruction. >> schifrin: garrett graff, matt olsen, thank you very much to both of you. >> thanks. my pleasure. >> woodruff: the impoverished nation of yemen stands on the brink of collapse, with e worst humanitarian crisis in the world. three quarters of its 29 million people need humanitarian assistance. there are 1 million suspected cases of cholera. and 10,000 people have died in a brutal, three ilyear old car causing all the misery. o side of the war: shiite houthi rebels, a religious minority in yemen, backed by iran, who now control thea, capital, sannd the second largest port city, hodeidah. on the other side: t government forces of president abdrabbuh mansur hadi, and a coalition led by saudi arabia, ich includes the united arab emirates and the united states. a saudi-led air campaign has pounded houthi strongholds in the north, and cut off aid and food, driving many people south, homeless in their own land tonight, with the support of the pulitzer center on crisis reporting, special correspondent marcia biggs rep

here to unpack where the investigatn stands, and what questions still remain, i'm joined by garrett graff, author of the book, "the threat matrix: inside robert mueller's f.b.i. and the war on global terror." and matt olsen, he's a former federal prosecutor who directed the nati center under president obama. welcome to you both. thank you very much. >> thanks, nick. >> schifrin: this is going on year two o robert mueller's investigation. the president says robert mueller has exceeded his remeant. has he and why haven't we seen more conclusions. >> i don't think the special counsel has exceeded the ritm or scope of the investigation. if you look back at the document that set this inhe motion, department of justice authorized the special counsel to look at anything linked to the russia meddling in our election and matters arising out of that investigation. so it's a broad scope in fact addition, if you see what the special counsel hae done,s gone to the district of virginia, the judge there has approved the manafort investigation, and he's also referred matters out to other prosecutors' off

. >>> first, i want to bring in cnn's chief political analyst and garrett graff, author of the threat matrix. thank you all for joining us. good evening. gloria, i'm going to start with you. break down your new reporting for us. president trump's legal team preparing for a showdown with robert mueller. >> that's right. even perez, pamela brown and i are reporting they are thinking they're now going to face a potential subpoena from the special counsel. we've reported, "the washington post" first reported it this evening, that there was at least one meeting with the special counsel and his then attorney john dowd in which the special counsel raised the potential of a subpoena and john dowd got very angry about it. and now the legal team understands that they've got a president who is angry after the michael cohen raid, who went from, yes, i'd like to testify to, no, i'm not going to testify. they have new members of their legal team who have to get sort of read in and caught up. so they're not making any blanket predictions here about what will occur, but they do believe that it's very