The chairman of Nebraska's Republican Party predicts that Sen. Ben Nelson's decision to back sweeping health care legislation will be his downfall. "I think this is the end of his political career in the state of Nebraska,” says Mark Fahleson. On Saturday, the state party launched a Web site, givebentheboot.com, to collect funds to oust the Democrat in the 2010 election. Nelson said earlier Saturday that he decided to support the measure after winning concessions to limit the availability of abortions in insurance sold in newly created exchanges, as well as tens of million in federal Medicaid funds for Nebraska....