The liberal group Change Congress unveiled an ad campaign on Thursday against Sen. Ben Nelson (D-Neb.) for his opposition to government-run health care. Nelson, a moderate Democrat who has said he is opposed to inclusion of a public plan in the health care reform legislation, immediately struck back. A press release sent out by Nelsons office referred to Change Congress as a special interest group and urged Nebraskans not to fall for the organizations claims.These people have a political agenda and that has nothing remotely to do with helping Nebraskans get and keep affordable, high quality health care, Nelson spokesman Jake Thompson said in a statement.Change Congress announced Thursday that it was sending a direct-mail piece to 3,000 Democratic donors across Nebraska urging them to withhold political donations to Nelson unless he changes his position on heath care and supports a government-run option as a part of a reform bill. The group also revealed that it was spending a modest $10,000 to distribute a Web ad.The groups mailer makes note of political contributions that Nelson has accepted from insurance companies and insinuates that his relationship with the insurance industry is the reason he opposes a public plan as a part of health care reform.Will Ben Nelson sell out Nebraska, the mailing asks, or support reform for our families?The mail piece also urges a donor strike against Sen. Mike Johanns (R-Neb.) and Members of the House and Senate broadly if they dont share Change Congress views on health care reform. The insurance industry has a strong presence in GOP-leaning Nebraska.Change Congress ad campaign against Nelson is built around Lincoln resident and self-described Eisenhower Republican Allen R. Schreiber, who claims he had to shut down his small business after private health insurance companies denied coverage to his five employees. Schreiber also refers to himself as a Nelson voter.Change Congress was founded by Stanford Law School professor Lawrence Lessig and Democratic political consultant Joe Trippi. The group operates both as a 501(c)3 and 501(c)4.On Wednesday, the conservative group Patients United Now launched a television ad campaign in eight states, including Nebraska, with the aim of influencing moderate Senate Democrats such as Nelson to oppose a public plan. Senate Democratic leaders are planning to mark up a health care bill in June, and they favor including a public plan in the legislation, as does the president. Most Republican Senators and several centrist Democrats have express reservations about including a government-run option in the bill.