President Barack Obama will participate via live webcast in Organizing for America’s “call parties— on Tuesday, encouraging supporters to keep the pressure on Congress to overhaul the health care system.“President Obama will be joining your party via an exclusive live Webcast to encourage your guests and thank you for your role in passing health reform,— OFA President Mitch Stewart said in an e-mail to members of the grass-roots organization.The parties are part of an effort by the OFA to generate 100,000 calls to Congress in a single day.“These call parties couldn’t come at a more important time — the final Senate committee just passed their version of the plan, so the debate is about to move to the full Congress for the first time,— Stewart writes. “And the insurance industry lobby is throwing everything they’ve got at us to distort the issues and derail progress. Our voices must be heard.—The OFA, an offshoot of Obama’s 2008 presidential campaign, is run out of the Democratic National Committee.