In last night’s debate, Mitt Romney made a new boast about his record on job creation at Bain Capital.

“[I]n the business I had, we invested in over 100 different businesses and net-net, taking out the ones where we lost jobs and those that we added, those businesses have now added over 100,000 jobs.

“I have a record of learning how to create jobs.”

When George Stephanopoulos pressed a little on this point, Romney said he’s a good “numbers guy,” and insisted the “over 100,000” figure was accurate. He added, “[T]here’s a steel company called Steel Dynamics in Indiana, thousands of jobs there. Bright Horizons Children’s Centers, about 15,000 jobs there; Sports Authority, about 15,000 jobs there. Staples alone, 90,000 employed.”

This is largely the basis for Romney’s entire presidential campaign, so it’s important to understand the extent to which he’s trying to deceive the public.

First, when Romney rattles off the jobs created by these companies, he’s referring to jobs that were created after he left his own private-equity firm. For him to take credit for them is, at best, a misleading stretch.

Second, Romney is making it sound as if he alone turned those companies into success stories — and that’s just not the case. Staples and Sports Authority, for example, had several other outside investors.

But the real problem here is Romney’s claim about “net” gains. To hear him tell it, if we added up all of the jobs gained through his investments, and subtracted all of the jobs lost through his investments, the result would show “over 100,000” gains.

Offering a detailed response is, as a practical matter, impossible — neither Romney nor his firm has provided enough information to do that kind of analysis. If it were true, presumably Romney and/or Bain would want to help prove the candidate right, and release the data to bolster the boast, but so far, the evidence is nonexistent. We’re apparently supposed to take Romney and his campaign’s word for it.

But that’s also impossible because Romney and the Romney campaign are now contradicting each other. Last week, the Republican’s chief spokesperson said the “over 100,000” figure is based on some companies that created jobs after Romney left Bain, but it simply excludes all job losses from the equation. As of last night, Romney is arguing that his own campaign is wrong, and the figure is a net figure.

Which side should we believe, Romney or the Romney campaign? I don’t know, but one of them isn’t telling us the truth.

It’s easy enough to resolve the controversy. All Romney has to do is offer a detailed disclosure and let us do the arithmetic. It’d be pretty easy to substantiate the claim with the relevant information.

What do you say, Mitt?

Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.