About the best that can be said about the Republican attacks on Mitt Romney’s record at Bain Capital is that President Obama is going to do the same thing eventually, so GOP primary voters might as well know what’s coming. Yet that hardly absolves Newt Gingrich, Rick Perry and others for their crude and damaging caricatures of modern business and capitalism.

Bain’s business model is little more than “rich people figuring out clever legal ways to loot a company,” says Mr. Gingrich, whose previous insights into free enterprise include years of defending the taxpayer-fed business of corn ethanol.

A super PAC supporting the former House Speaker plans to spend $3.4 million in TV ads in South Carolina portraying Mr. Romney as Gordon Gekko without the social conscience. The financing for these ads will come from a billionaire who made his money in the casino business, which Mr. Gingrich apparently considers morally superior to investing in companies in the hope of making a profit.

Mr. Perry, who has no problem using taxpayer financing to back his political allies in Texas, chimes in that “I have no doubt that Mitt Romney was worried about pink slips, whether he was going to have enough of them to hand out. Because his company Bain Capital, with all the jobs that they killed, I’m sure he was worried he’d run out of pink slips.”

Politics isn’t subtle, and these candidates are desperate, but do they have to sound like Michael Moore?

We have our policy differences with Mr. Romney, but by any reasonable measure Bain Capital has been a net job and wealth creator. Founded in 1984 as an offshoot of the Bain consulting company, Bain Capital’s business is a combination of private equity and venture capital. The latter means taking a flyer on start-ups that may or may not pan out, something that neither Mr. Gingrich nor Mr. Obama seem to find offensive when those investments are made by Silicon Valley firms in “clean energy.”

One Bain investment during Mr. Romney’s tenure was to back an entrepreneur named Tom Stemberg, who was convinced he could provide savings for small-business owners if they were willing to shop at a store instead of taking deliveries. Today, the Staples chain of business-supply stores employs 90,000 people.

Bain also backed a start-up called Bright Horizons that now manages child-care centers for more than 700 corporate clients around the world. Many other venture bets failed, but that’s capitalism, which is supposed to be a profit and loss system.

Boston Globe via Getty ImagesMitt Romney at Bain’s offices in Copley Plaza in 1990.

The loss part is what seems to trouble the Gingrich-Perry-Obama critics, especially in Bain’s private-equity business. Like some 2,300 other such U.S. equity firms, Bain looks to buy companies that are underperforming or undervalued and turn them around.

Far from “looting,” this is a vital contribution to capitalism and corporate governance. One of the persistent gripes of the left is that too many CEOs make too much money even as their companies flounder. Private-equity firms target such companies or subsidiaries, replace their management, and try to unlock the underlying value in the enterprise.

Private equity helps to promote dynamic capitalism that creates wealth, rather than dinosaur capitalism of the kind that prevails in Europe and futilely tries to prevent failure. Sometimes this means closing parts of the company and laying off employees, but the overriding goal is to create value, not destroy it.

A Wall Street Journal news story this week reported that Bain in the Romney era differed from many equity firms in buying more young and thus riskier companies. This contributed to a higher rate of bankruptcy or closure—22%—for companies held by Bain after eight years.

Bain disputes the Journal’s calculations, but one test of overall success is whether investors keep entrusting a firm with their money. Mr. Romney and his colleagues raised $37 million for their first fund in 1984. Today, Bain Capital manages roughly $66 billion. Its investors include college endowments and public pension funds that have increased their investments in private equity to get larger returns than stocks and bonds provide. The people who benefit from those returns thus include average workers.

Bain’s turnaround hits include Sports Authority and tech-research outfit Gartner Inc., which was once a small division of an advertising firm and is now a public company worth more than $3 billion. Another success was Steel Dynamics, which used Bain money to build a new steel factory and now employs 6,000 people.

The tougher questions for Mr. Romney involve the cases in which Bain took early payouts in dividends and management fees after purchasing existing businesses that ultimately went bankrupt. There are several in this category, including another steel company called GSI, though its hundreds of job losses were far fewer than the jobs created at Steel Dynamics.

The medical-equipment maker once known as Dade International is now much larger than it was when Bain bought it in the 1990s. But Mr. Romney’s company later sold its stake, and heavy debts taken on during the Bain years forced Dade to spend two months in bankruptcy in 2002 and cost 2,000 jobs. The company later resumed its rapid growth, and Siemens bought it in 2007 for $7 billion.

Certainly Bain Capital made sure that its investment partners were paid first, but the larger truth is that the invisible hand worked pretty well. Notice that because the overall job statistics for Bain investments are by all accounts positive, many critics attack the Romney record with claims about private equity in general. The left is cheering a study commissioned by the Census Bureau that found that companies bought by private-equity firms suffer more job losses soon after a buy-out than similar firms that didn’t experience buy-outs.

But this is hardly surprising since the companies were acquired in part because they were underperforming. The critics also don’t mention that the Census study found that firms acquired in private-equity transactions created more new jobs in the ensuing decade. Imagine what might have happened if Chrysler or GM had been bought by private equity two or three decades ago. They might have been turned around much earlier, at far less pain to fewer workers, and without any taxpayer cost.

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The larger political point is that Mr. Romney has a good story to tell if he is willing to elevate this ugly rumble into a debate over free enterprise and America’s future. This is not Mr. Romney’s strength, as he prefers to talk in personal terms (“I’m an optimist!”) or to lapse into his default mode as the corporate technocrat. This invites personal attacks in return and it leads him into mistakes like this week’s gaffe that “I like being able to fire people who provide me services.”

Mr. Romney needs to rise above the personal and base his claim to office on a defense of the system of free enterprise that has enriched America over the decades and is now under assault. Mr. Obama will attack Mr. Romney as Gordon Gekko because the President can’t win by touting his own economic record. Mr. Romney’s GOP opponents (with the admirable exception of Rick Santorum) are embarrassing themselves by taking the Obama line, but Mr. Romney should view this as an opportunity to stake his campaign on something larger and far more important than his own business expertise.