WASHINGTON — Hoping to push their agenda ahead of the presidential election, a group of prominent conservatives has devised a 121-page policy manifesto aimed at giving the Republican Party a message that will attract some of the middle-class voters the party lost in recent White House races.

The document, to be unveiled Thursday, features eight essays with proposals on issues including health care, taxes and education. The authors hope the book will help Republicans address the economic anxieties of Americans and nudge the party from its most polarizing positions and constant confrontations with President Obama.

“We have to do more than ‘Stand athwart history, yelling stop,’ ” said Pete Wehner, a conservative scholar, referring to William F. Buckley Jr.’s vision for National Review, the conservative magazine he founded.

“Sometimes you have to do that and then try to bend history in a different direction,” said Mr. Wehner, one of the contributors to the manifesto.