WASHINGTON - When Missouri Sen. Jim Talent rolled out his first television campaign ad, the beleaguered first-term Republican focused on a simple message: "It's not what you promise that matters. It's what you do."

It's a point that neatly defines the rhetorical battle that has broken out between the two political parties now that Congress has recessed until early September.

As lawmakers embark on a frenzied month of campaigning ahead of November midterm elections, the record of what the GOP-controlled Congress has done -- and not done -- is shaping up as a central dispute in the fight for control of Capitol Hill.

In the face of failures to clear major legislation on several fronts -- including immigration, military tribunals and ethics reform -- House and Senate Republicans are tirelessly talking up other achievements, such as tax breaks and support for domestic security.

Democrats, smelling victory this fall, are sharpening their attacks on a majority they equate with the infamous Republican "do-nothing Congress" that President Truman successfully used as a foil in his 1948 campaign.

With voters in a sour mood, the minority party is increasingly banking that disappointment with what Congress has accomplished will be their ticket back to power. Democrats need to pick up six seats in the Senate and 15 in the House to claim the majority in each chamber.

In Missouri, Talent's Democratic opponent, Claire McCaskill, is hammering the incumbent for voting against increased federal funding for embryonic stem cell research -- a popular measure that foundered when Congress failed to override President Bush's veto of it. According to some polls, McCaskill now has the lead in the closely watched race.

"The Democrats have the congressional Republicans on the run," said Don Kettl, a University of Pennsylvania political scientist who focuses on public policy. "The Democrats can't win with a 'do-nothing Congress' charge alone. But it adds to the drumbeat of their campaign that Republicans can't govern. And so far it's paying off."

But whether it provides the payoff Democrats are hoping for on Election Day remains very much in doubt. They have tried unsuccessfully before to ride the "do-nothing" message to victory, most recently in 2004, when Republicans actually expanded their majorities in both congressional chambers.

And even as popular discontent with the war in Iraq, President Bush and the Congress mounted, the party for months struggled to refine its pitch, trying a succession of slogans before rolling out the "do-nothing" campaign.

"It's amazing," said Joe Garecht, a Pennsylvania political consultant who has worked for Republican candidates. "This year presents [Democrats] their best chance in over a decade for re-capturing the House of Representatives, yet they can't pull together and develop a simple, coherent, and courageous message. . . . What are we left with? Vague notions of 'do-nothingness,' some talk of a 'culture of corruption.' "

Still, the notion that the Republican Congress is failing is underscored this year by a dearth of breakthroughs on some of the biggest issues of the day, longtime observers say.

Lawmakers are at loggerheads over how to overhaul the nation's immigration policies, with Republicans disagreeing among themselves about the proper approach to dealing with millions of illegal immigrants in this country.

Congress has not developed a system for prosecuting terrorist suspects, despite a recent U.S. Supreme Court decision rejecting the Bush administration's current use of military tribunals.

No major reforms to the Social Security system, identified last year by the president as a pending crisis, have been enacted.

And there has been no significant reform of ethics guidelines for Congress, despite pledges from Republican lawmakers in the aftermath of the scandal centering on lobbyist Jack Abramoff that exposed a web of unseemly influence peddling on Capitol Hill.

It isn't a very impressive record, said Ross K. Baker, a political scientist at Rutgers University in New Jersey who has studied Congress for 30 years.

"The big successes were almost entirely in the area of personnel," most significantly the confirmation of two Supreme Court justices, Baker said. "On the whole, the main courses never made it to the table and the nation had to be content with side-dishes."

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