Six Republican senators voted on Wednesday against an amendment to permanently extend the expiring Bush-era tax cuts.

A group of GOP centrists voted down a measure sought by Sen. Jim DeMint (R-S.C.) to set in stone current tax rates.

Sens. Scott Brown (Mass.), Susan Collins (Maine), Mark Kirk (Ill.), Lisa Murkowski (Alaska), Olympia Snowe (Maine) and George Voinovich (Ohio) all bucked DeMint on a procedural vote to suspend Senate rules and allow for the amendment.

One Democrat, centrist Sen. Ben Nelson (D-Neb.), voted with all the other Republicans to extend the expiring tax cuts.

As things stand, the current tax deal would only extend income tax rates for two years, in exchange for an extension in unemployment insurance and other middle-class tax breaks.

The two-year extension by itself comes with a considerable price tag, but it doesn't compare to the hole in the deficit a permanent extension might threaten. Extending the tax cuts for top earners alone would cost $700 billion over the next 10 years.

Conservatives like DeMint contend that the money belongs to taxpayers, and shouldn't be counted the same as deficit spending. The DeMint amendment, which needed 67 votes in this procedural count, failed 37-63.