Moveon.org issued a warning Tuesday to any Democrat who might join Republicans to filibuster a government-run insurance option -- if you oppose the government option you will lose support from the organization's 5 million members

Senate Majority Leader Harry Reid announced Monday that the Senate's version of a health care reform bill will include a so-called public option. Moveon.org issued its e-mail to its supporters threatening revolt one day later.

The group said it surveyed its members over the weekend and found that "93 percent of MoveOn members agreed that any senator who helps block an up-or-down vote on a health care bill with the public option should lose the support of all five million of us -- no donations, no volunteering, and no help getting out the vote."

To ensure conservative Democrats will not oppose the public option, the group is launching an "emergency campaign" to urge them to support an up-or-down vote.

Despite its support, the group added that Reid's bill is still problematic.

"The 'opt-out' version of the public option has real problems," the e-mail said, adding that "the most conservative states in the country would likely opt out, potentially leaving millions of uninsured folks without access to the affordable health care a public option would provide."