Nightly News | September 01, 2013
>>> tonight is presenting new evidence that sarin gas was used in a chemical attack in syria, as it tries convince congress to authorize a military strike there it's unclear if lawmakers will approve the request when they return next week from recess, but already, the decision to ask for support has had ripple effects both here and around the world. we have complete coverage tonight and we begin with nbc's kristen welker at the white house . kristen, good evening.
>> reporter: carl, good evening to you. the decision to give congress a vote is a political gamble by president obama . one white house official tells me the strategy moving forward will be to flood the zone and that effort started today with the chief of staff, vice president and president making a flurry of phone calls to lawmakers and other top officials holding a rare holiday briefing today on capitol hill . with the president's credibility on the line, secretary of state john kerry fanned out on the sunday shows, revealing new evidence, further bolstering the case for military action .
>> hair samples and blood samples have tested positive for signatures of sarin. so this case is building and this case will build.
>> reporter: administration continued its push with an unusual classified briefing to lawmakers on capitol hill today, more than 100 turned out, despite the holiday weekend.
>> i think members of congress were divided.
>> reporter: the developments cap a stunning turn of events. the president spent a week indicating a military strike was imminent, sending out secretary kerry to make the case and ordering navy warships to be ready. but on saturday, mr. obama hit the pause button.
>> i will seek authorization for the use of force from the american people 's representatives in congress .
>> reporter: according to senior administration officials, despite the public ramp-up, president obama debated seeking congressional support all week and without a broad international coalition, feeling isolated, aides say it was the no-vote in the british parliament that largely swayed him.
>> the nos have it.
>> reporter: the president went for a walk with the chief of staff on the white house grounds and decided he wanted congress to be on record and share the responsibility. he called a meeting in the oval office that lasted two hours with some of his closest advisers expressing shock and opposition, but by saturday, they were on board. today, secretary kerry indicated did he not feel undermined by the president and put on a united front .
>> david, let me be pre blunt. i do not believe the congress of the united states will turn its back on this moment.
>> reporter: but this morning, lawmakers previewed the contentious battle to come.
>> this is a clear failure of leadership.
>> this is a national security issue. this isn't about barack obama versus the congress .
>> there's weakness here on the part of the president.
>> i think it's a mistake to get involved in the syrian civil war .
>> if i had to walk over to the capitol right now, i would pull out my voting card and vote no.
>> i would vote yes because the whole world is watching and so is iran.
>> congress overrules a decision of the president of the united states on an issue of national security , that could set a catastrophic precedent in the future.
>> reporter: analysts say the president is taking a political risk .
>> if he gets fired down, it could be the talk of a lame duck presidency.
>> reporter: senator patrick leahy told reporters today the president's resolution will be amended because it's too broad. officials here say they aren't surprised. the white house outreach continues. the president will hold conference calls and meetings with lawmakers this week. carl?