Senator John McCain, R-Ariz., says Republicans valued "power over principle" and paid a "heavy price" for that in the mid-term elections.
As Democrats prepare to take control of Congress, McCain tells NBC's "Thursday" show he's "very sad" his party lost both chambers.
House Democrats Thursday will elect Nancy Pelosi the country's first female speaker.
They're also are planning quick legislative action on legislative priorities that include boosting the minimum wage and stem cell research.
Democrats also want a vote on new ethics rules that would ban gifts from lobbyists and clamp down on travel funded by private interests.
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They've said they won't allow Republicans the chance to amend any of the first half-dozen bills to be brought to a vote during the first 100 hours of the new Congress.