PHOENIX - The Discount Tire chain faces a boycott by Latino advocacy groups after several Valley stores posted "Re-Elect Sheriff Joe Arpaio" signs in their windows.

The boycott, organized by Puente and Somos America, will be announced at a news conference Thursday at the Discount Tire store at 3rd Street and Baseline Road in south Phoenix, according to a spokeswoman for Somos America.

A protest outside a Discount Tire store in west Phoenix is planned for Saturday.

Latino leaders say Discount Tire blew it by using its stores to campaign for Arpaio, the most divisive figure in Arizona politics.

Social media erupted last week after customers saw "Re-Elect Sheriff Joe Arpaio" signs in store windows. It's not clear how many of the company's 49 stores in Maricopa County posted the signs.

"It's a good opportunity for our community to say to businesses: 'No, no, no,'" said Phoenix attorney and activist Danny Ortega.

Ortega said he was outraged by Discount Tire's public support for a sheriff widely viewed as an enemy of Latinos.

"Every business ought to be very cautious about how they make a public display -- an in-your-face display -- of who they support," Ortega said.

The protest has gone beyond social media.

"We know that they have been bombarded by email, social media, also other pressures," said Pita Juarez, of the One Arizona Coalition.

Discount Tire founder Bruce Halle's $6 billion fortune makes him the richest person in Arizona. Arpaio has collected $25,000 in campaign cash -- four donations for the maximum amount -- from Halle and his wife, and from another couple connected to his company.

Public opinion analyst Michael O'Neil said Discount Tire's public display of support for Arpaio was news because companies rarely do that for a candidate.

"It's pretty rare because any business runs the risk of alienating customers and nobody wants to do that," O'Neil said.

Ortega agrees Discount Tire has a right to declare its support for a candidate. He concedes that other businesses he patronizes might support politicians he doesn't care for.

"The hot button here is Sheriff Joe Arpaio," said Ortega, who was a regular customer at Discount Tire's South Phoenix store before he learned of the campaign signs.

His message to company executives: "You are supporting that candidate in the face of how he has treated our community? I'm taking my business elsewhere."

It appears stores have taken down the Arpaio campaign signs in response to the backlash. The nationwide chain's stores are company-owned.

Discount Tire did not respond to numerous requests for comment.

Bruce Halle and his wife, Diane, as well as his company, have donated millions of dollars over the last decade to countless causes.

Discount Tire was one of the top donors to Gov. Doug Ducey's Prop 123 campaign last spring, with a $1 million campaign donation.