Jerry Kronenberg writes in the Boston Herald that former U.S. Senate hopeful Steve Pagliuca is touting one-time rival Martha Coakley’s job-creation credentials, but a new study questions his own firm’s ability to turn companies around.

Moody’s recently ranked Boston-based Bain Capital – where Pagliuca serves as a managing director – the fifth-worst major private-equity firm in terms of buying businesses and saddling them with risky debts.

“Companies sponsored by (Bain) performed poorly during our study,” Moody’s wrote in its report. Pagliuca – who lost to Coakley in last week’s Democratic primary for the late Sen. Edward M. Kennedy’s seat – has since endorsed his ex-rival.

“Martha (has) a very strong jobs plan that will get people to work,” the Bain executive said yesterday during a campaign stop with Coakley at Lawrence clothing maker Polartec.

Moody’s found that 45 percent of 22 companies Bain bought in recent years have either defaulted on debts or run a high risk of doing so. For instance, radio giant Clear Channel Communications, which Bain and Boston’s Thomas H. Lee Partners bought for $26.7 billion last year, is a “likely candidate for restructuring or bankruptcy,” researchers wrote.

THL Partners, the only other Hub firm included in the Moody’s study, ranked third from the bottom.

Moody’s listed 55 percent of THL’s recent acquisitions in default or distress – a finding the firm disputes. THL claims the report has several errors, including a failure to count at least seven healthy companies in the mix.

Private-equity firms borrow big bucks to buy businesses, putting the resulting debts on the books of companies they buy. That means that, while private-equity firms own the businesses, the companies they’ve bought must actually pay creditors back.

Critics say this means workers and lenders – not private-equity investors – suffer if businesses fail because of excess debt.

“As companies become more distressed, one way they cut costs is through layoffs,” said Josh Kosman, author of “The Buyout of America: How Private Equity Will Cause the Next Credit Crisis.”

Kosman and others argue private-equity firms took advantage of a 2005-07 drop in interest rates to make deals that stuck businesses they bought with lots of debt. These companies could fail when the loans come due in a few years, critics charge.

Kosman said at least six businesses Bain bought in the past have gone bankrupt – including Dade International, a deal Pagliuca personally oversaw.

Private-equity firms dispute Moody’s report. Among other things, the industry claims the study wrongly labeled some businesses in default merely for taking advantage of this year’s market meltdown to buy back their debt at bargain prices.

“Half of (the) defaults captured by Moody’s are not (true) defaults,” the Private Equity Council wrote in a critique of the study.

A Bain spokesman said Moody’s “misrepresented the solid overall health and market leadership of (our) companies.”

DDIFO’s  editors note: Bain along with Lee Partners and the Carlyse Group own Dunkin Brands