Left have, since formation of the UPA Government, been threatening the Government. Only some of the times the Government have conceded the Demands of the Left. The Congress have heeded to such demands from other parties as well.
But certainly, by showing to outside world that the government was listening to these demands, and painting these as unjust demands, the congress has been cleverly steering through these road blocks.
Signing of the Document is considered to be helping the Congress Party in the next Elections. And the same is believed to be murdering the prospects of the Left parties in general. BJP is opposing to it because their advantages would also reduced to a great extent if the deal is signed before the Election. It is needless to say that BJP will surely be signing the deal if it is not signed by the present government, anyway.
The Price Rise is a sore throat that is threatening to implode. The Congress can't wait for that opportune moment that may never come. They have few solid issues for the impending election. Those may erode over time.
The Congress has taken a calculated risk by not heeding to the Blackmail. Surely the Party will try to bake the Cake and will share it with no one else. Not even with its allies. Left will try very hard to project that the Deal was not in the interest of the country, with not much effect. With Oil Price soaring, the public opinion against the deal has melted down a bit. BJP surely, will play it down.