The grass-roots group Organizing for America is activating its membership in 33 districts that voted for President Barack Obama but are represented by Republicans, asking them Saturday to demand that their GOP Representatives support the Democratic-backed health care reform bill.

“The House of Representatives is set to vote on real health insurance reform as early as this evening, and your representative, Rep. [XXX], faces a stark choice: Vote with their district and support the bill, or stand with the insurance companies and oppose,— states a copy of the e-mail, which is signed by OFA Political Director Addisu Demissie. “Make sure [the Representative] hears from you, and gets a reminder that their district voted for this change just 12 months ago,— Demissie writes. “With the big vote happening in as a little as a few hours, there’s not a moment to lose. Please call right away.—

The effort is being launched even though no Republicans are expected to support the House bill. The House Republican Conference Saturday afternoon voted unanimously against the rule for debating the bill.

OFA has at least 13 million members and was built off the massive e-mail list assembled by Obama’s 2008 presidential campaign. It is run out of the Democratic National Committee.