Seldom, for any president, has there been so wide a gap between the magnitude of achievement and the measure of the polls. In any event, what the scholars of the next generation will credit to Barack Obama won’t be enough to mitigate Democratic losses in the midterm election.

The president has been vindicated in his decision to push for sweeping progressive change, culminating in Wall Street reform, in his first two years. Imagine trying to push that, or health care, or the largest economic package in history, or a wholesale revamping of the college loan program to benefit students instead of banks through a Congress that next year will have many more Republicans, more bitterness and more modest results.

FDR and Reagan didn't shy from ideology; they proclaimed it.

No wonder the advocates of action on climate change and energy, the orphans of this transformative time, have been left to rage against the waning of the congressional session. With everything to play for between now and November, Democrats will move quickly from the final passage of legislation to the final weeks of campaigning. What case will they make to voters frustrated by a recovery slowed by insufficient stimulus?

The president can argue, correctly, that he averted a depression—and technically, that the recession is over. But job creation lags, more so than usual this time as the impact of premature fiscal contraction in Europe—the very policy the GOP favors here—depresses global growth. It’s not exactly a ringing appeal for Democrats to say that things could be so much worse. And experience teaches that fleeing the central issues and relying on the political patent medicine of localized races is a prescription for losing.

The White House obviously realizes this. The president has been road-testing a message designed to cast the midterms not as a referendum but as a choice. In essence, he describes the choice as future versus past: Bush and the Republicans caused the mess, so don’t give them the chance to do it again. This is relatively free of ideological content — and it could prove powerful, even devastating in 2012, if Americans see the economy moving steadily ahead. But present circumstances — three in particular — demand a more ideological approach.

First, blaming Bush won’t turn the tide, and not just because the 24-hour news cycle conditions the public to expect instant results (as we’ve seen with the oil spill). The crash came during the twilight of the Bush presidency, so Obama doesn’t have the breathing space of FDR, who came to office after three years of Herbert Hoover and the Great Depression. Americans, who had endured so much for so long, accepted the notion that FDR’s turnaround would take awhile.

Bush should be part of the 2010 narrative, but only within a larger context: He made the wrong decisions because he was on the side of vested interests, not ordinary people who are now paying the price. That highlights where the Republicans still are. It’s a defining difference between the parties. Without it, assailing Bush just sounds like an excuse.

The second flaw in a non-ideological strategy is related to the first. Unless they cast themselves as fighters against powerful forces holding people back, Obama and the Democrats, who are actually changing the country, can too easily be recast as the status quo that deserves to be overthrown. This is not the inevitable price of incumbency, as FDR and Ronald Reagan showed from different ends of the spectrum. In office they remained outsiders, tribunes of grievance and hope, by insistently standing for something larger than a transactional politics. Rather than shying from ideology, they proclaimed it. It was for this reason that one of them could repeatedly and profitably invoke the specter of Herbert Hoover, and the other could do the same with Jimmy Carter.

Third, Obama has to re-energize a discouraged Democratic base, which now appears less likely to vote in November. This requires an appeal to values, not just a comparison of results — because for some time to come, the legislative record, however impressive, will far outpace the results in people’s lives. The Obama voters of 2008 need to see the president and his party fighting not just on issues, but for a cause. Extended unemployment compensation, new measures to create jobs, some form of cap-and-trade, immigration reform, and the repeal of “don’t ask, don’t tell” — Democrats won’t win on most of this, but that shouldn’t be the end of the story. 

In 1962, JFK narrowly lost the battle for Medicare. He then campaigned against Republicans on the issue — which is one reason why the party of an incumbent president registered a rare degree of midterm success that year.

The Obama legions of the last election are likely to shake off their lethargy and fully enlist in this midterm if the president and Democratic candidates draw the dividing lines in states and congressional districts coast to coast.

We know this president has the capacity to mobilize the English language — and the voters. He can command the public square — and yes, dominate it and define the election — if he leads people to ask the fundamental question: Who’s on your side?

And he has plenty of evidence to make his case, including a rich trove provided by the Republicans — from Texas Rep. Joe Barton’s comment about the $20 billion White House “shakedown” of poor BP to Arizona Sen. John Kyl’s absurd contention that tax cuts for the rich don’t have to be paid for, but help for the jobless does. Such examples are not blunders but revelations, providing a window into the soul of a Republican Party that at every turn stands for power and privilege. The GOP’s populist protest is nothing more than a veneer for policies that serve the few at the expense of the many. The veneer must be stripped away; the dots must be connected; the narrative must be told.

When the Chamber of Commerce charged this week that Obama has “vilified” business, White House Chief of Staff Rahm Emanuel and Senior Advisor Valerie Jarrett shot back in a letter: “We will not … accept the lax regulation of the financial industry … [or] stand by while oil and gas companies continue to fight needed changes to outdated regulations that are partially responsible for one of the worst environmental crises in American history.”

Too wordy, but it’s the right message. That message must be repeated day after day until Election Day — and not just from staff or surrogates, but from the campaigner-in-chief. Only he can shift the ground of the election to the true fault line of our politics, turning the country away from the Tea Party’s fake and bitter brew to what the November election can and should be about: Who will fight for you?

If the President and his party do this, they will still lose seats in Congress. But they will hold more of them. Along the way, Obama will also lay the foundations for a re-election in 2012 that stands for something — and leads, as Ronald Reagan’s did after a perilous midterm passage, to a realignment of American politics.