Bragging about what they’ve achieved is what incumbent politicians do.

Ronald Reagan brought morning to America. Nelson Rockefeller, running for his fourth term as governor of New York in 1970, had a snappy slogan: “He’s done a lot. He’ll do more.” British Prime Minister Harold Macmillan told voters in the late ’50s they “never had it so good.”

But as Democrats struggle to hang on to the Senate this year (and try against the odds to take over the House), they are not in the usual boasting mood.

Some of the party’s candidates actively praise the Affordable Care Act, but others talk more about how they would fix it. Most Democrats hailed this month’s excellent jobs numbers, but much of their message this year stresses a squeezed middle class and the problems of stagnating wages and economic inequality. “You’ve never had it so good” is not in their talking points.

More than anyone, President Obama can expound on how much better things are now than they were when the economy was near collapse in 2009. But a campaign speech he offered at a Democratic fundraiser last week in La Jolla, Calif., nicely captured the party’s two-track argument.

Yes, he began by accentuating the positive. “When I came into office, the American economy was in a freefall that people don’t still fully appreciate,” Obama said. “And by most measures, what we’ve accomplished together as a country over the last five years has been significant: 9.2 million new jobs, an auto industry that has come roaring back, a financial system that’s stabilized, trillions of dollars of wealth recovered and restored because housing came back and people’s 401 pensions bounced back.”

It’s a lot of good news. But note that word “significant.” It’s less buoyant than, say, “fantastic” or “wonderful.” The understatement reflected what Obama said a moment later: “What we also know is that the American public is anxious.”

The president listed the many sources of that anxiety, concluding with a central Democratic theme: that “for a couple of decades now, even when we’re growing, even when corporate profits are soaring, incomes, wages have not gone up.” For “ordinary Americans,” he said, the improvement “hasn’t translated into greater financial security.”

Obama’s be-happy-but-worry theme is justified by the facts, but it leads to a peculiar imbalance in the campaign dialogue. Republicans rail against everything Obama has done. Their agenda may look like a catalog of Fox News obsessions — last month it was Obamacare, currently it’s Benghazi. But they will not stop blaming Obama and his party for all the country’s shortcomings. Democrats, by contrast, feel constrained from offering an unambiguously sunny rebuttal.

The long-term stall in middle-class incomes Obama described is one reason they can’t. Most Democrats also have a philosophical commitment to reducing inequalities. They may hold the White House but they are not championing the status quo.

The party’s candidates fear that if they are too upbeat, they’ll look out of touch with a country whose spirits aren’t very high. The RealClearPolitics polling averages show that over the last month, only 28 percent of Americans saw the country as being on the right track; 63 percent said it was moving in the wrong direction.

“It’s not a contradiction, but there is a tension between the administration wanting to argue for success on health care and the economy and House and Senate candidates who want to identify with the many voters who are still struggling in the economy,” said Anna Greenberg, a Democratic pollster with many clients on the ballot this fall. “And many of the independent expenditure groups will be talking about the Koch brothers and other big-money groups on the right who are tilting Washington against the interests of average people.”

A lot of this Democratic advertising will be directed at Republicans who control the House and have blocking power in the Senate. Placing the burden for Washington’s failures on Republicans and their big funders is a necessary element of any Democratic campaign. It will be especially persuasive on an issue like the minimum wage. But this is not the same as making a positive case that could ease the electorate’s overall alienation.

Reality is what reality is, and it will take many more months of growth to change the country’s disposition. But even as Democrats respond to widespread discontent, they also need to convince Americans that Obama’s tenure gives them a good deal to cheer about. Doing both at once is more challenging than incessantly repeating the word “Benghazi.”

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