Hayworth announced his decision at his Phoenix campaign headquarters, accompanied by Maricopa County Sheriff Joe Arpaio and Chris Simcox, co-founder of the Minuteman Civil Defense Corps, a volunteer group that works to prevent illegal U.S. border crossings, the Phoenix News Times reported.
Simcox once said he would challenge McCain, the 2008 Republican presidential nominee, but he abandoned his campaign Monday to support Hayworth.
At about the same time Hayworth was making his announcement, McCain had his own campaign event in Tempe, Ariz., the newspaper said.
A Rasmussen poll in November indicated McCain and Hayworth in a dead heat but a more recent poll by Public Opinion Strategies, a Republican political affairs research firm, indicated McCain held a substantial lead over Hayworth, who served in the House of Representatives from 1995-2007.
The Arizona primary is in August.