DeMint resigns from US Senate The senior Tea Party-backed politician in Congress has resigned from the US Senate to run a leading Washington-based think-tank amid continuing upheaval in the conservative ranks following Barack Obama's re-election as president. Jim DeMint, from South Carolina, said he was leaving to run the Heritage Foundation, a powerful conservative think-tank that has close relations with like-minded members of Congress. Mr DeMint's departure comes amid difficult budget negotiations over the US fiscal cliff, $600bn worth of tax increases and spending cuts that are triggered on January 1 unless the White House and Republicans can reach a deal. Mr DeMint sharply criticised the Republican leadership in Congress this week for its budget proposal to Mr Obama, offering extra tax revenues, even though they are gained through the close of loopholes rather than by lifting rates. It is not the only reason why many Republicans may be happy to see the back of Mr DeMint, who angered colleagues in the last two elections by backing and funding extremely conservative candidates to run for the Senate, with disastrous results. In both 2010 and 2012, Republicans failed to gain control of the Senate when they were well positioned to win, in large part because a number of DeMint-backed candidates were judged by voters to be outside the mainstream. "If you want to propel forward your agenda, then the Senate is not going to be a happy place for you," said a senior Republican aide in Congress. In an interview with the Financial Times last year, Mr DeMint said his main focus was getting more staunch conservatives into the Senate to harden the "jello" in the middle of Republican ranks. Although his departure may help at the margins in the budget negotiations, Mr DeMint's new position gives him a powerful perch from which to pressure Republicans in Congress to adhere to policies he supports. Republicans nerves are fraying over the fiscal cliff talks, as many worry Mr Obama is depicting successfully their opposition to higher tax rates on the top 2 per cent of income earners as a gift for the wealthy. "At present, any reading of the headlines over the past week indicates that Republicans are fighting to protect the rich and cut benefits for seniors," said Bobby Jindal, the Louisiana governor, in an article for Politico. It may be possible to have worse political positioning than that, but I'm not sure how. Mr Obama and John Boehner, the Republican house speaker, spoke by phone on Wednesday about the fiscal cliff, but spokesmen for neither would provide details of the conversation. It was their first conversation in a week.