The Senate rejected the "Buffett Rule," which would've raised the tax rates for millionaires, after Republicans accused President Barack Obama of pitting Americans against each other.

Democrats argued that it was time for the tax code to treat the wealthy and the middle class fairly, but were unable to get enough votes to have the rule clear the Senate. The vote was mostly along party lines.

A day before Americans' taxes were due at the Internal Revenue Service, the partisan clash previewed themes that will echo throughout this year's presidential and congressional election campaigns. But while the two parties competed for the stronger message to voters, one thing was sure — Republicans had enough votes to derail the Democratic bill.

As debate began, Senate Majority Leader Harry Reid, D-Nev., said the gap between the wealthiest Americans and everyone else had grown into a gulf.

"They shouldn't be allowed to hide behind tax loopholes that rig the system in their favor," Reid said.