. >> what about europe? >> i am not taking cards off the table. i'm not going to use nukes but i'm not taking any cards off the table. >> the trouble is the sane people hear you and the insane people are not affected by your threats. >> i think they're more effective than you might think. >> okay. your call. much more from the university of wisconsin green bay and our msnbc exclusive town hall with donald trump coming back.

. >> how about europe? we won't use in the europe? >> i won't take it off the table for anything. >> you might use in the europe? [ laughter ] >> no. >> i'm just saying -- >> i'm not taking cards off the table. >> one of the many headlines yesterday, the msnbc town hall with donald trump as chris matthews talked to him there. the republican front-runner refusing to rule out using nuclear weapons in europe, joining us now economist jeffrey sachs, he's advised bernie sanders' presidential campaign on foreign policy. >> that's a great way to start the day, huh? >> your first blush reaction to that? >> well, it's horrifying. you know, he's scaring the wits out of everybody, i think here and abroad and it's very flippant and not very serious.

. >> how about europe, we're not going to use it in europe? >> i'm not going to take it off the table. >> you're going to use it in europe? >> no, i don't think so. >> well, why don't you just say it? i'm never using a nuclear weapon in europe. >> i am not taking cards off the table. >> you can catch the rest of that trump town hall right here on msnbc, that's at 8:00 p.m. right after john kasich at 7:00. we'll be right back. a fair pric, and that horrible smells are really good at hiding. oh, boy. there it is. ♪ ohh. ooh. [ gags ] so when you need a house cleaner or an exterminator, we can help you get the job done right, guaranteed. get started today at angie's list, because your home is where our heart is.

. >> how about europe? >> i'm not going to take it off the table? >> you're going to use it in europe? >> no, i don't think so. i'm not taking cards off the table. i'm not going to use nukes, but i'm not going to -- >> the same people hear you, and the insane people are not affected by your threats, that's the trouble. the real fanatics say keep it up. >> i think they're more affected than you might think. >> you're call. much more from the university of wisconsin green bay, our msnbc exclusive town hall with donald trump coming back. jack be nimble, jack be quick, jack knocked over a candlestick onto the shag carpeting...

. >> europe? >> i'm not going to take it off the table. >> you might use it in europe? >> no. i don't think so. >> just say it. i'll never use a nuclear weapon in europe. >> i am not taking cards off the table. >> so, michael, that is where resume matters or the ability to have a team around you and do the studying needed, gain the knowledge needed to be able to answer questions as chris posed to the front-runner. >> you're exactly right, tamron. and in this regard, it's not a resume of i've done this as governor, i've done this as chairman of the house budget committee which john kasich was. it's i've cared about these issues, i have cared enough to think about them, to be involved in them. ted cruz has a very thin resume and he right now winning and winning big in wisconsin. the reason he is is because

. >> how about europe? you won't use it in europe? >> i am not taking cards off the table. >> it wasn't just the issue of abortion that donald trump made headlines on last night in that town hall with chris matthews. he also told chris that the use of nuclear weapons is still on the table, refusing to rule them out, even in europe or the middle east. now this comes as president obama is hosting 56 world leaders for a two-day summit aimed at stopping the spread of nuclear weapons. nbc's ron allen live at white house where international motorcades are lining up. tell us about this meeting. what are they trying to accomplish here? >> well, mr. trump also said

. >> you might use it in europe? >> no, i don't think. so. >> well, change it. >> i'm not taking the cards off the table. >> well, this comes as -- after trump told "the new york times" he would use nuclear weapons only as a quote, absolute last step and he said he supported the idea of japan and south korea developing their open nukes. a reversal of the nuclear disarmament. >>> later today leaders from 50 nations will gather in washington on preventing nukes from falling into the hands of terrorists. the president is out with a "washington post" op-ed where he says the u.s. is is on track to

. >> what about europe? >> i am not taking cards off the table. i'm not going to use nukes but i'm not taking any cards off the table. >> the trouble is the sane people hear you and the insane people are not affected by your threats. >> i think they're more effective than you might think. >> okay. your call. much more from the university of wisconsin green bay and our msnbc exclusive town hall with donald trump coming back. bleach

. >> what about europe? >> i am not taking cards off the table. i'm not going to use nukes but i'm not taking any cards off the table. >> the trouble is the sane people hear you and the insane people are not affected by your threats. >> i think they're more effective than you might think. >> okay. your call. much more from the university of wisconsin green bay and our msnbc exclusive town hall with donald trump coming back. hey buddy, you're squashing me! liquid wart remover? could take weeks to treat.