A proposal to implement the Buffett Rule was blocked in the Senate on Monday, but proponents of the millionaire tax vowed to keep the issue alive in the months ahead.

Republicans, as expected, garnered enough support to reject Democrats' attempt to bring up the proposal for debate. The Democrats fell nine votes short.

The GOP put the kibosh on the bill known as the "Paying a Fair Share Act," which embodies President Obama's proposed millionaire tax.