WASHINGTON  With Republicans mobilizing against the proposed health care overhaul, President Obama, Congressional Democrats and leading advocacy groups are laying the groundwork for an August offensive against the insurance industry as part of a coordinated campaign to sell the public on the need for reform.

The effort will feature town-hall-style meetings by lawmakers and the president, including a swing through Western states by Mr. Obama, grass-roots lobbying efforts and a blitz of expensive television advertising. It is intended to drive home the message that revamping the health care system will protect consumers by ending unpopular insurance industry practices, like refusing patients with pre-existing conditions.

“I think what we want to communicate is that this is going to give people who have insurance a degree of security and stability, the protection that they don’t have today against the sort of mercurial judgments of insurance bureaucrats,” said David Axelrod, a senior adviser to Mr. Obama, adding, “Our job is to help folks understand how this will help them.”

Revamping health care is the president’s top legislative priority, and people on all sides of the debate agree that August, when lawmakers leave Washington to take the pulse of constituents, will be crucial to shaping public opinion. With Republicans making headway by casting the legislation as a costly government takeover, Democrats have decided they must answer the question on the minds of those now insured: “What’s in it for me?”