The stakes could not be higher for this president. We're a little more than 48 hours away now until president obama addresses the nation in primetime over possible military intervention in syria. Tonight, the administration has revealed new and disturbing images of the chemical weapons attack against civilians, that the president says the world must respond to. Inside the white house this evening, the president and his team preparing that address, as they continue to work the phones, calling members of congress, who they are still trying to convince. President obama has addressed the country just two times from the oval office in primetime. It is unclear where in the white house he'll deliver that message tuesday night. It will be a challenging sell. Protests this weekend across the country and around the world. Lawmakers getting an earful. We've shown you the images of SENATOR john McCain getting push-back from his constituents in tucson. Abc's senior washington correspondent jeff zeleny starting us off from the white house tonight. Reporter: In the most consequential campaign of his second term, tonight, president obama is losing. His bid to launch limited military strikes against syria, colliding with a wave of public apprehension and congressional opposition. Syrian president bashar assad issued a new denial tonight of using chemical weapons and in an interview with charlie rose, airing monday night on pbs, assad is quoted as pledging some kind of retaliation, if a strike is made. This, as the white house is mounting an unprecedented 48-hour push to make its case. The president's chief of staff appearing on all five sunday talk shows. I've been talking to dozens of members of congress, not a single one of them so far has rebutted the intelligence. Should there be consequences for his having used gases, chemical weapons, to kill more than 1,000 of his own people, including more than 400 children? Reporter: The president will deliver a personal pitch monday in six network television interviews on the eve of a primetime address to the nation tuesday. Senior administration officials tell abc news it is increasingly an uphill fight with congress. They have no viable plan for success. Reporter: While some republicans are on board -- I think the president has made the decision correctly. Reporter: While senate approval is still within reach, an abc news survey finds well over a majority, 231 lawmakers, in the house, are firmly opposed or leaning against military strikes. And on the home front, we found anxiety. We can do something. But that doesn't mean we have to bomb the hell out of the country. I don't believe that assad's allies will sit by and allow us to bomb them without some retaliation. And you're going to see more terrorist attacks here. Reporter: As the obama administration this weekend used newly released gruesome videos of syrian victims to prove its case to congress, assad denies any knowledge of chemical weapons. And jeff zeleny joining us from the white house now. Jeff, you learned from your sources a short time ago that the president plans another rare step in making his case? Reporter: That's right, david. After making phone calls all weekend, president obama is going to capitol hill in person for a rare face to face meeting with senate democrats. He's really trying to win over those wavering democrats who are hearing an earful from their constituents. It's on the eve of the senate vote scheduled to begin wednesday.