With 79 percent of precincts reporting, Democrat Harry Mitchell had 44,523 votes, or 52 percent. Hayworth had 38,283 votes, or about 45 percent. Libertarian Warren Severin had 2,814 votes, or about 3 percent.
In 12 years in Congress, Hayworth had faced mostly weak attempts to unseat him. He had never won by less than 48 percent of the vote and has easily won re-election the last three times.
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But Mitchell, a former state senator and former Tempe mayor, closed in during the final weeks in a race characterized by increasingly nasty attack ads.
Dan Dolan, an independent from Scottsdale, said he votes based on the candidate, and that's why he voted for Mitchell.
"I don't like the Bush crowd," he said. "We're in a war we shouldn't have been in."
Dolan said he also differs with Hayworth on the immigration issue.
"I think there's a better way to do it than building a fence," he said. "Look at Berlin. What good did that wall do?"
Republican Malyn Kain of Scottsdale said she cast a ballot for Hayworth because her Navy soldier son is serving in Iraq.
"We need to stay the course," she said. "I think our representation has been good. Our gas prices are down, our economy is up. Scottsdale is booming and so is all of Arizona."