WASHINGTON (AP) — The Senate is ready for a tax-cut showdown that is all about Democrats and Republicans showing voters their differences over taxing the well-off and blaming the other side for threatening to push the government over a fiscal cliff.

Senators planned to vote Wednesday on a $250 billion Democratic measure to extend expiring tax cuts next year for all but the highest earners.

Democrats need 60 votes to advance the proposal, which they don't have. It seemed unlikely there would be a separate vote on a GOP bill extending everyone's tax cuts, which also would lose.

If the two sides don't compromise, $600 billion in tax increases and spending cuts for 2013 would be triggered — the so-called fiscal cliff, which analysts say would jar the weak economy.