Carly Fiorina is the new "it" candidate in the Republican presidential field, following a second straight sterling debate performance at the Ronald Reagan presidential library Wednesday night.

But there was a moment in the debate that previewed a major potential weakness for Fiorina. It came when moderator Jake Tapper noted that Donald Trump had said Fiorina "ran HP into the ground" during her time as CEO. Fiorina responded, "I led Hewlett Packard through a very difficult time, the worst technology recession in 25 years," adding: "We had to make tough choices, and in doing so, we saved 80,000 jobs, went on to grow to 160,000 jobs."

Trump -- and Tapper -- largely let the issue drop. But Fiorina's past political history suggests that her struggles at HP could be a campaign killer.

In 2010, Fiorina was running surprisingly close to California Sen. Barbara Boxer (D), who was struggling in a strong election cycle for Republicans nationally. Then, Boxer ran this ad focused on Fiorina's time at the helm of HP.

In 2010, Carly Fiorina ran against California Sen. Barbara Boxer (D), who was struggling in a strong election cycle for Republicans. Boxer ran this ad against her. (Barbara Boxer/YouTube)

The commercial notes that Fiorina laid off 30,000 workers at HP while feathering her own nest (the ad's narrator says she tripled her salary) and buying a "million-dollar yacht" and "five corporate jets." It went up on TV in the middle of September and effectively ended Fiorina's chances.

Look at this chart, via Real Clear Politics, documenting the polling averages for the entirety of the Boxer-Fiorina contest.

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See how the red line starts dropping precipitously right around mid-September?  That's not a coincidence.  The ad functioned as a sort of knock-out punch for Boxer even in a year where Republicans claimed victories all across the country.

Now, California's general electorate is not the same as the Republican presidential primary electorate. And Fiorina has had five years to think of better responses than she had in 2010 to attacks on her record at HP. (For what it's worth, I thought her response Wednesday night was very solid.)

But nothing can or will change the facts in the Boxer ad. PolitiFact has truth-squadded the commercial and found the claims in it to be "mostly true." And with the growing inequity between the haves and the have-nots in the U.S. already established as a front-burner issue in both parties, the attack is likely to be particularly cutting for Fiorina.

With success in politics comes further scrutiny. Fiorina got off relatively easily Wednesday night, but if she continues to move up in the polls, you can expect to hear a lot more -- from her opponents and in super PAC ads -- about her record at HP.  The question for her is whether the issue -- and the ad -- remains a campaign killer or whether she can find a way to defuse its power.