Republican leadership in Congress would reverse generations of progress in the U.S., DNC Chairman Tim Kaine will charge Wednesday in a speech.

Kaine, the Democratic National Committee (DNC) leader, will sharpen his rhetoric against Republicans in what's being billed as a "major national address" this afternoon in Philadelphia.

In that speech, Kaine will warn of even sharper changes for the country if Republicans were to take control of Congress in this fall's elections.

"The Republican Party doesn’t just want to go back to the 'exact same agenda' they pursued during the Bush years. They don’t just want to repeal the legislation President Obama and Democrats have enacted," Kaine will say. "They don’t just want to take away the changes you worked so hard to bring about. They want to take away the changes that your parents and grandparents and generations of Americans worked so hard to enact."

The former Virginia governor's stark warning comes as President Obama will also amp up his rhetoric against the GOP during a speech on the economy in Cleveland. The speech is specifically meant to target House Minority Leader John Boehner (R-Ohio), who blasted the administration's handling of the economy in Cleveland just weeks earlier.

Kaine's speech also serves to underscore a message that Democrats have sought to drive home as the election season begins in earnest: Republicans would move the country backward while Democrats would push forward with progress.

However, the sharpened rhetoric in Obama and Kaine's speeches might reflect concern that their warnings of the consequences of Republican rule are falling flat.

At least one poll released Tuesday suggested voters are unconvinced that GOP wins this fall would mean a return to the economic policies of President George W. Bush, a refrain echoed constantly by Democrats. Fifty-eight percent of registered voters said in an NBC/Wall Street Journal poll that they believe Republicans would bring different ideas to the table, while 35 percent say GOP control of Congress would mean more Bush-era policies.

But Kaine will name GOP leaders (including Boehner) and candidates whose proposals, the DNC chairman will charge, would slash social programs and threaten jobs.

"On Election Day, it will be Americans’ turn to choose. They can choose Republicans who drove our country into a ditch," he'll say. "Or they can choose Democrats who are helping us climb out of that ditch. Who have taken the bold actions necessary to repair the damage caused by nearly a decade of failed Republican leadership."