Back in the dog days of George W. Bush's second term, when each month seemed to bring new lows for the president's approval ratings, there was almost always this consolation: The surveys would show that Congress was even less popular than he was.

In general, that's going to be the advantage an executive enjoys over a collective body such as a legislature. Hence the decision by Barack Obama to take a page out of Harry Truman's 1948 playbook and campaign for re-election against a "do-nothing Congress." Given his record, it may be his wisest course.

It's also a gift to Republicans—if the party's presidential nominee has enough wit to turn it to his advantage.

Let's take the politics first. However useful the "do-nothing Congress" theme may be for Mr. Obama, it's not exactly a ringing endorsement of Harry Reid in an election when the Democratic majority he enjoys in the Senate is up for grabs. To the contrary, it opens the door for Republicans to turn the tables in a way that squeezes Mr. Reid and his fellow Senate enablers: between a Democratic president attacking them implicitly, and a Republican presidential contender attacking them explicitly.

Ed Gillespie, a former chairman of the Republican National Committee who was a colleague in the Bush administration, sums up the challenge this way. "Our nominee," he says, "needs to talk about the do-nothing Senate, and remind voters that Harry Reid and the Democrats are in control there. Republicans need to constantly remind voters that the problems in our economy and with the health-care bill are the result of Democratic control—and that in the Senate this control continues to block reform and advance the Obama agenda."

Senate Majority Leader Harry Reid (D., Nev.) European Pressphoto Agency

The good news is that the Republican contenders are mostly in a good place to advance this argument. As a former leader in the U.S. Senate, Rick Santorum no doubt understands how important a majority in the Senate would be to a GOP president. So does Newt Gingrich, who had his own experience with the Senate leadership when he served as speaker of the House.

For the Romney campaign, this line of attack might be even more fruitful. For the most part, Mr. Romney has campaigned as a former business executive and Beltway outsider who can get things done. The president, however, is not a CEO with everyone else in Washington under his direction—and going after Mr. Reid's do-nothing Senate would be a good sign that Mr. Romney understands that.

Manifestly there's no shortage of material. Under Mr. Reid's leadership, the Senate has not passed a budget resolution in three years. It has never voted to extend the payroll tax cut for a full year—which Vice President Joe Biden says is the administration's No. 1 economic priority. Nor did it protest when the president made a controversial recess appointment when the Senate plainly was not in recess.

The one notable area where Mr. Reid did not "do nothing"—ObamaCare—is not pretty. It would be good for Republicans to remind the public of this record. Partly it involved a complete rewrite in Mr. Reid's backroom, along with notorious vote-buying deals to secure enough votes to prevent a GOP filibuster, including the Louisiana Purchase ($300 million in Medicaid funds for the home state of Sen. Mary Landrieu) and the Cornhusker Kickback ($100 million in Medicaid funds for Nebraska's Sen. Ben Nelson).

The point is that with the exception of ObamaCare and the stimulus, Mr. Reid's energies have been exercised largely to prevent action, not take it. Remember Mr. Obama's jobs bill, and how he called on Congress to "pass this bill now"? When Senate Republicans pushed for a vote, Mr. Reid responded by changing the rules of the Senate to prevent one.

Over in the House, meanwhile, Republicans have been a hive of activity. Currently some 30 pro-growth bills languish in Mr. Reid's do-nothing Senate, lest the buck ever be passed to the president's desk. These include measures reflecting proposals endorsed by the President's Council on Jobs and Competitiveness—ranging from regulatory reform and tax simplification to reducing our dependence on foreign sources of energy.

For the past two years, House Republicans have used their majority to block further expansion of the Obama agenda. They have also come up with real alternatives that they know will likely be vetoed by the president or stalled in the Senate. That too is part of the groundwork for this November's elections. For the message they are sending is that if you want change in Washington, you need more than a Republican-controlled House.

By adopting the do-nothing Congress meme, Mr. Obama implies that Mr. Reid and his Senate Democrats have failed. Memo to Messrs. Romney, Santorum and Gingrich: Now's the time to make that point from the right.

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