Chris Woodyard, Charisse Jones, and David Jackson

USA TODAY

WASHINGTON -- Ivanka Trump’s fashion line has suffered a setback. And boy is Dad mad.

President Trump took to Twitter on Wednesday to complain that his daughter has been "treated so unfairly" by the Nordstrom (JWN) department store chain, which says it will no longer carry her fashion line.

Once again raising questions about mixing politics and the family's businesses, Trump wrote, "My daughter Ivanka has been treated so unfairly by @Nordstrom. She is a great person -- always pushing me to do the right thing! Terrible!"

Parents are often, and understandably, protective of their children and often step into defend them when they believe they are wronged. But when the parent is the President of the United States, the way Trump responded raises more than eyebrows.

To be sure, Trump is not new to criticizing businesses using the social media platform. The Nordstrom comments mark the latest Twitter blast from Trump, who has also taken numerous companies to task. Most, over business matters that Trump perceived as being in the interests of jobs for Americans, like when he criticized Ford and Toyota over plans for plants in Mexico, or Boeing, for what he believed was too high of a projected price tag for the next Air Force One.

But the Nordstrom tweet raises ethics concerns because it involves his daughter's business. Trump's critics said the president has, again, used his position to threaten businesses in an unfair and perhaps illegal manner. In a tweet of his own, Norm Eisen, chief ethics officer for President Obama and co-founder of the organization Citizens for Responsibility and Ethics in Washington, broached the idea of a lawsuit.

Nordstrom said in a statement Wednesday that the decision made public last week to drop the fashion line was about falling sales.

"To reiterate what we’ve already shared when asked, we made this decision based on performance," Nordstrom said. "Over the past year, and particularly in the last half of 2016, sales of the brand have steadily declined to the point where it didn’t make good business sense for us to continue with the line for now."

The chain went on to say that it has a "great relationship with the Ivanka Trump team" and that they have talked about the issue with them over the past year, including personally informing Ivanka Trump last month.

Trump didn't elaborate on what was unfair about Nordstrom's action, though White House spokesman Sean Spicer later said the president was responding to "an attack on his daughter," and "he has every right to stand up for his family." The president's tweet didn't appear to hurt Nordstrom financially. After initially dropping 1%, Nordstrom shares rose more than 4% for the day to close at $44.53, up $1.75.

Nordstrom is not the only retailer that is making changes in regard to Ivanka Trump's brand.

TJX, owner of Marshalls and T.J. Maxx, told informed staff members last week that they should blend Ivanka Trump products with other store merchandise, rather than featuring it on its own.

The stores will continue to sell Ivanka Trump products, TJX spokeswoman Doreen Thompson said in a statement. But "from time to time, we communicate with our stores about how to handle merchandise. The communication we sent instructed stores to mix this line of merchandise into our racks, not to remove it from the sales floor.”

Ivanka Trump's fashion line includes shoes and accessories along with jewelry and apparel. As a private company, Trump's brand does not have to release information about its revenue. But a brand spokesperson said Wednesday that revenue for the 2016 fiscal year was up 21% over 2015.

In July, Forbes reported that GIII, the licensing partner for Trump's clothing line, said that the apparel brand earned $100 million in revenues in the most recent fiscal year.

Online traffic to Ivanka Trump product pages on Nordstrom’s website dipped by roughly 14% in December and January, according to Jumpshot, a marketing analytics firm. But sales of her merchandise may not be hurting everywhere. Sales of her merchandise at Macy’s had a roughly 18% increase in those months, according to Jumpshot.

Surging interest in Ivanka Trump’s brand might lead Macy’s to stick by it, says Randy Antin, Jumpshot’s vice president of marketing. However, online visits do not necessarily translate into sales. Web “traffic is an indicator,’’ says Antin, “but it’s not necessarily what a company will (use to) make its business decision.’’

In November, Nordstrom Co-President Pete Nordstrom sent employees a memo after the election in which he said the controversy over Ivanka Trump merchandise, which it has carried since 2009, had put the chain in a tight spot.

He said Nordstrom makes a "sincere effort not to make business decisions based on politics but on performance and results," but that "we find ourselves in a very difficult position." He did acknowledge, however, that the Ivanka Trump line of shoes had sold well.

At least two members of Nordstrom’s board of directors backed Democrat Hillary Clinton over Trump in the 2016 presidential election, Federal Election Commission records show.

Erik Nordstrom, a co-president of the company, contributed $2,700 to the Hillary for America campaign fund in March 2016. Shellye Archambeau, the Metricstream CEO appointed to the Nordstrom board in February 2015, gave $1,000 to Hillary for America in September of that year, according to the contribution records.

Kevin McCoy contributed to this report from New York.

Woodyard reported from Los Angeles, Jones from New York and Jackson from Washington