Giuliani was joined by his wife, Judith, as he surveyed the podium at the Republican convention Tuesday.

ST. PAUL, Minnesota (CNN) – Former New York Mayor Rudy Giuliani is expected to come out swinging Wednesday, in a “compelling speech” intended to contrast the stark differences between presumptive Republican presidential nominee John McCain and his Democratic rival Barack Obama, a McCain campaign official told CNN.

“It’s red meat in the sense that it’s a very strong argument on why McCain is the better choice,” said the official, who previewed Giuliani’s address before the Republican National Convention.

Former governors and GOP presidential rivals Mike Huckabee and Mitt Romney are also expected to address how McCain differs from Obama. With a critical look at Democrats, the speeches will address "why Washington’s broken" and how Republicans "must fix it."

“The speeches will be a little edgier tonight,” the official told CNN. Tonight, McCain will officially be nominated for the GOP nomination.

With speeches from Meg Whitman, former president and CEO of eBay, and Carly Fiorina, former chairman and CEO of Hewlett-Packard, early in Wednesday night’s program, McCain officials say there will be a “big concentration on economic issues.”

While Whitman and Fiorina will not cover any new policy ground, the themes will “echo” McCain’s May speech entitled “2013,” where the Arizona senator maps out his first term achievements by 2013. Among the successes McCain envisions, “several years of robust economic growth” and winning the war in Iraq.