Let us now praise Nancy Pelosi.

Long after the midterm stories have faded, and the predictions of the president’s political demise prove as facile and false as they were with Ronald Reagan and Bill Clinton, history will accord Pelosi an unprecedented scale of achievement for a House speaker. The breakthroughs of the past two years bear her indelible stamp. She has been not only the master of the House, but a moving force in changing America for generations to come — and despite their fulminations, the GOP that has demonized her will not succeed in undoing those changes.

It was Pelosi, in a meeting with President Obama after Republican Sen. Scott Brown’s election in Massachusetts, who rebuffed Rahm Emanuel’s argument that comprehensive health reform couldn’t pass, so Democrats should retreat to a modest bill that focused on expanded coverage for children. "What makes you think I would support that?" she bluntly asked. Pelosi understood, as did Obama, that Democrats had to act in this session of Congress — or forfeit for another decade or more the chance to move decisively toward health care as a fundamental right of all Americans. She then persuaded her members to live with the Senate version of reform, and to trust that the filibuster-challenged body would pass the necessary amendments.

It was a legislative tour de force from someone who plainly believes that the purpose of politics goes beyond serving the self-interest of politicians. From the stimulus that averted a second Great Depression to Wall Street reform to the transformation and expansion of college student aid, Pelosi and the president have written more landmark legislation than anyone in nearly half a century. Majority Leader Harry Reid did his best in the sclerotic Senate, and at critical moments change squeaked by the Republican blockade.

Would Democrats have fared better Nov. 2 if they had been more cautious?

In many instances the change Pelosi initiated in the House fell short in the Senate — from climate change and energy security to the repeal of “don’t ask, don’t tell.” But what did reach the president’s desk will lift the lives of hundreds of millions of Americans — and the credit belongs not just to Obama, but to Pelosi and the colleagues she persuaded to take the risk of their convictions. Not for her, tokenism and triangulation.

The sweep of the change made her a trademark target for Republicans, who smeared her personally — she was called “a traitor,” and worse — just as they lied about health reform, the stimulus, and the bipartisan bailouts that prevented global financial collapse. The cheapest attacks were steeped in a sexism that mirrors the racist tinge of the anti-Obama Tea Partiers, touching a responsive chord among those who can’t abide an America where power is no longer the preserve of white men (albeit with set-asides for the Sarah Palins and Sharron Angles and Clarence Thomases).

If the Democratic base had voted, the party might have kept the House, or come close to it. I had hoped — and predicted — that the base would confound the turnout models. It didn’t, and the blame game has begun. But much of what is being said of Nov. 2 contains elements of truth: The message was too soft-edged; the White House was too complacent for too long in combating the GOP’s blizzard of lies; the president should have shown the country he was focused on jobs, jobs, jobs — perhaps with a monthly report from the Oval Office on the economy. This might have established some basic truths — for example, that the deficit this year is actually lower than last.

One person who can’t be blamed is Pelosi. There was no way for her to dominate the dialogue and set the terms of choice. But to save Democratic seats, she worked until midnight day after day until Election Day. What else was she supposed to do — give up health reform or give in to the financial speculators in an attempt to hold on to power? Expediency wouldn’t even have been good politics. How would Democrats have fared on Nov. 2 if they had shied away from an $800 billion stimulus — and the unemployment ditch was 3.5 million jobs deeper?

The conservative Blue Dog Democrats who took the timid, waffling course that critics suggest Pelosi should have followed lost more than half of their members. They surely deserve this fate after making the stimulus too small and fighting to water down everything else, including their own campaigns, which they ran as quasi-Republicans. (One of them, Mississippi Rep. Gene Taylor, cravenly told his constituents that he had voted for McCain; his district responded by voting him out.)

There are also ineluctable realities in American public life that faced the president, the speaker, and Democrats generally. First, a period of sweeping change — even and especially change that lasts — inevitably generates a backlash. Thus LBJ passed Medicare and Medicaid, the Voting Rights Act, federal aid to education, and immigration reform in 1965 and 1966, and promptly lost 47 House seats. Second, a bad economy is bad for incumbents; just ask Reagan's people about 1982. Even an economy on the mend is of little avail if voters don’t yet feel the uplift in their own lives; just ask Clinton about 1994. A calculated caution that proposed only mini-progress during the past two years wouldn’t have changed the outcome; it would have made it worse.

Finally, Pelosi didn’t have Harry Reid’s good fortune. Democrats still control the Senate because extreme GOP nominees were exposed and defeated — from Delaware to Colorado to Nevada. Forty-four Tea Party candidates who captured House seats didn’t face the same level of scrutiny in the media. They were able to hide their stripes while “independent” committees, turbocharged by anonymous corporate donations and managed by nonpartisan do-gooders like Karl Rove, relentlessly attacked their opponents. (The 82 tea-baggers who were defeated in House races were mostly in true blue redoubts like California, New York, and Massachusetts — or in heavily Democratic districts elsewhere.)

If he doesn’t succumb to the siren song of Blue Dogs and the establishment commentariat, donning the transparently inauthentic garb of political opportunism, Barack Obama will be re-elected in 2012 — and probably by a wide margin. Nancy Pelosi won’t be re-elected speaker in January. But whatever lies ahead for her, she already has played an honorable and indispensable role in forging a new future for America.