"Pushing" is a wrong metaphor here - a better one is "chasing after." Presidential politics is like farming. You do not sow in November - you harvest what you sowed in the Spring. Likewise, you do not set a new agenda three weeks before the election, but instead you harvest your support - as much as you can.
So Kerry is doing the right thing - he is appealing to the voters by adjusting his campaign promises to what voters want to hear instead of the other way around - trying to adjust the voters to his campaign promises. It is the right strategy, because (i) going the other way around is a sure way to lose, and (ii) campaign promises doe not matter that much, if at all, what matters is power politics taking place after the election.
Campaign promises may be important to ideologues and zealots, but they do not matter to anyone else. The reason is that unlike ideologues and zealots who use one frame of reference for every situation, most people use different frames to understand different issues, and what is relevant in one frame, is usually not relevant in another. Bush promised not to involve the US troops in "democracy building" in Haiti, when he was campaigning against Gore, but then he committed the troops to democracy building in Iraq. And the reason that this apparent inconsistency is not notices even by his opponents is that Iraq and Haiti are understood through very different frames (war on terrorism vs. humanitarian assistance) - so there is no contradiction.
Wojtek