On Friday, a day after the Democratic convention is set to end with Obama’s speech, the monthly jobs numbers are set to come out. According to Politico, the Romney campaign is already salivating at the chance to use bad economic news to overshadow the message and enthusiasm coming out of the convention.

The Romney camp will do this by citing the “net” jobs lost on Obama’s watch, to portray the President’s tenure as a job-destroying one:

Romney spokesman Ryan Williams said the campaign will use the jobs numbers to remind voters of Obama’s economic record, including the August 2011 jobs report, which counted zero new jobs.
“Barack Obama is the first president in modern history to preside over a net job loss, and we intend to highlight the failure of his economic policies during and after the convention,” Williams said.

Politico let this pass with no comment or context, so let me supply some. The Romney campaign’s calculation of this “net job loss” number under Obama is reached with a metric that includes the hundreds and hundreds and hundreds of thousands of jobs that the economy was bleeding during Obama’s first months in office, before his policies took effect. And yet, if you look at the quote above closely, you’ll see that the Romney campaign is citing that number as proof that those same policies have failed.

The key is that Romney needs to use this metric to suggest that jobs were destroyed on Obama’s watch, even though we’ve seen over 20 consecutive months of job creation. In other words, without factoring in the huge numbers of jobs lost before the policies took effect, the Romney campaign can’t portray them as a job-destroying failure.

Post fact checker Glenn Kessler has repeatedly called out Romney’s use of this metric. CNN has also done excellent work blowing up this tactic. (The Romney campaign has openly said it doesn’t see fact checking as a legitimate constraint, so perhaps it’s not surprising that the bogus metric is back from the dead.)

That’s not all. Romney’s own advisers have explicitly said it would be unfair and misleading to judge his record with this metric. When the Obama campaign was slamming Romney for presiding over the 47th-worst-in-the-nation job growth as governor of Massachusetts, Romney adviser Kerry Healey repeatedly said it was unfair and misleading to use ”one number” or an overall “average” to sum up Romney’s jobs record, arguing that the trajectory over time is more significant. Yet the Romney campaign is again using “one number” — the net jobs lost — to indict Obama’s entire record. (Fixed.)

More broadly, in 2004, during George W. Bush’s reelection campaign, Romney said that it was absurd to hold Bush responsible for the “slowdown in jobs” during the “early years of the Bush administration,” blaming it instead on outside factors. Romney said the American people would dismiss this argument as “poppycock.”

Romney’s claim that Obama presided over a “net” loss in jobs will be central to the ferocious spin war that will erupt after the Dem convention and the Friday jobs report, and voters will be buffeted by competing claims as they enter the final process of choosing their president. Will news orgs give their readers and viewers the facts and context that will enable them to understand what Romney is actually saying here?