On Monday, hours after The Post reported that Fiorina's 2010 Senate campaign mismanaged its finances and delayed paying its debts for years, the former Hewlett Packard CEO said the outlet had lost its "credibility."
"I don't think the Washington Post has much credibility anymore," Fiorina told reporters, adding that The Post "also said I wasn't a secretary."
That was a reference to the paper's recent "fact check" which gave the Republican candidate "three Pinocchios" for claiming that she began her career as a secretary as part of her personal narrative of achieving success in the corporate world. The Post was forced to issue a lengthy explanation for its fact check last week after overwhelming pushback from readers.
Finally, Fiorina's campaign posted an item to its website on Monday blaming the "liberal media" for a double standard: Hillary Clinton had taken four-and-a-half years to pay off $25 million in campaign debt and received scant coverage, the item argued, whereas Fiorina had taken less time to pay off $500,000 in debt - a fraction of what Clinton had owed.
"The Washington Post takes two political candidates and reports in two very different ways," the campaign stated.
The candidate's return-fire on the Post may be more low-key than Donald Trump's dramatic off-and-on boycotts of Fox News, or the Hillary Clinton campaign's sustained war with The New York Times, which it sees as an overly aggressive antagonist, or even Marco Rubio's absence from CNN for nearly two months. Still, it has allowed Fiorina to pit herself against a beloved conservative bugaboo -- what she described on Monday as "the left and their allies in the media."
For its part, The Post not backing down from its story on Fiorina's campaign finances, which it says was based on more than two dozen interviews with former staff members, friends, contractors and operatives who worked on the 2010 Senate campaign.
"We stand by our story," Steven Ginsberg, the Post's political editor, said in a statement.
In the report, the Post claims that Fiorina failed to reimburse the widow of a former campaign staffer for her late husband's work. Fiorina owed the widow about $30,000, the Post's report claims.
"It was one of more than 30 invoices, totaling about $500,000, that the multi-millionaire didn't settle — even as Fiorina reimbursed herself nearly $1.3 million she lent the campaign," The Post wrote. "She finally cleared most of the balance in January, a few months before announcing her run for president."
In an email to CNN, Fiorina spokesperson Sarah Flores said the Post's report included at least one factual error and one dubious source.
"The story says 'most of the balance was paid off.' Not true. It has all been paid off," Flores wrote. Fiorina's FEC reports indicate that that is indeed the case.
The Post's report goes on to cite others who say they weren't adequately reimbursed by Fiorina's 2010 campaign, but Flores points out that at least one of the aggrieved, Jon Seaton, is a senior adviser to GOP presidential hopeful Lindsey Graham -- a connection that is not disclosed in the Post's article.
"You're interviewing political operatives claiming they're owed money and it didn't occur to you as a journalist to ask who they are currently working for?" Flores wrote in an email. "Or worse, they did ask...and just didn't disclose it?"
Ginsberg did not address the Graham connection.