They put off the deal for as long as it took to stay in power. Now that General elections are around and with runaway inflation getting worse and still slated to worse, Congress thinks this is the right time to bow out claiming a moral highground and also avoid the public ire over continuing inflation. They know that things will get worse nd if BJP wins more seats in coming state elecctions, Political pressure by allies and rising inflation will kill them completely. The current Nuclear deal cannot be legalized by Bush administration now and if Obama wins, the non-proliferation lobby will get more teeth to call it off. The damage is done. Jingoistic posturing now is more an attempt to divert public attention from inflation and washing one's hands off the responsibility in a face saver to minimize damage that they will suffer the next general elections.
