Maricopa County Sheriff Joe Arpaio talks to attendees of a meeting of the Surprise Tea Party in Surprise, Ariz., on Sept. 20, 2016. Arpaio is up for re-election in November.(Photo: Hannah Gaber, The Arizona Republic)

PHOENIX — The question dominating Maricopa County Sheriff Joe Arpaio’s closest re-election campaign in decades is whether a criminal contempt charge expected to be formally lodged against him in U.S. District Court will be a breaking point for voters or a call to arms.

Arpaio opponents hope swing voters will conclude he is unfit to lead a law-enforcement agency under a cloud of criminal prosecution. Supporters point to the speed and timing of the move — on the eve of early ballots going out — as proof Arpaio, a Republican, is the victim of an attack by President Obama’s administration.

In any other election year, a criminal charge against Arpaio would shift the race to his opponent, Democrat Paul Penzone, said Shane Wikfors, a GOP campaign operative and former Arizona Republican Party spokesman.

But in 2016, when many voters nationally seem eager to defy a system they believe is rigged, it could be seen as political targeting and backfire on Democrats, he said.

“The strange thing is, we’re kind of in a culture of non-‘law and order,’ so I wouldn’t be surprised if Arpaio’s supporters would disregard it and still vote for him” in large enough numbers for victory, Wikfors said. “It doesn’t matter what the law says at this point. We are in such a dysfunctional political environment that either side will view it from their own perspective.”

The sheriff’s high name-recognition and a $1.2 million warchest, four times as large as Penzone’s, are helpful, Wikfors said.

But Arpaio’s age — 84,  while Penzone is 49 — and voters’ desire for “new blood” after 23 years in office could hurt his chances, Wikfors said.

Pressure from mainstream Republicans also could mount for Arpaio to retire for the good of the party, he said, much as GOP leaders have called on Donald Trump to drop out of the presidential race after a video surfaced of Trump talking about groping women. Some leaders see Arpaio’s widespread alienation of Hispanics, one of the fastest growing U.S. demographics, as damaging to the party’s future.

“One of the sub-themes of this political year is the civil war in the party,” Wikfors said. “There are Republicans who consider themselves the more reasonable, party-growing type of Republicans, and they see Trump, and Arpaio at the local level, as individuals who are dividing the party and causing the party great havoc.”

But so far, only Democrats — including Phoenix Mayor Greg Stanton and Vice Mayor Kate Gallego — have publicly called for Arpaio to step aside.

But Republicans on the Phoenix City Council, Sal DiCiccio and Thelda Williams, said they supported Arpaio.

“I think he’s been unjustly pursued for enforcing a state law that some people didn’t like,” said Williams, who worked in Arpaio’s jail system from 1996 until 2007.

The anticipated criminal-contempt charge against Arpaio is the culmination of years of battles in federal court over Arpaio’s immigration-enforcement operations, which led to a racial-profiling lawsuit. Earlier this year, a federal judge found Arpaio in civil contempt for violating orders to reform his organization. The judge, a Republican appointee, asked federal prosecutors to consider criminal charges.

If Arpaio is charged, a trial is unlikely to finish before the election. It’s unclear whether the charge would be a felony or misdemeanor. If convicted, Arpaio could spend up to six months in jail. State law requires any public official convicted of a felony to step down.

Tight race for sheriff 

Polls since the summer have shown a tight sheriff’s race. But Wednesday, Republican consultant Gibson McKay released results from a survey conducted before Arpaio’s criminal hearing this week showing Penzone with a 10-point lead.

McKay surveyed 348 high-efficacy county voters Oct. 2-5, with a third of calls going to cellphones and two-thirds to landlines. The results are within a margin of error of plus or minus 5.2 percentage points.

Arpaio campaign spokesman Chad Willems questioned the quality of the poll and said the sheriff has always expected a close race.

But opponents are stepping up their efforts with “dark money” groups spending money on efforts to defeat Arpaio.

Petra Falcon, an immigration activist and longtime Arpaio foe, said voters will decide the sheriff’s fate.

“Arpaio has consistently abused the power of his office by wasting taxpayer resources, intimidating average citizens, harassing hardworking immigrants and their families, and seeking retribution against his critics,” Falcon said. “It is high time he learned that no one, not even Joe, is above the law.”

But Willems said that’s not the message voters will take away from a decision to prosecute.

“We believe that voters will see this latest action by the corrupt Department of Justice for what it is: A pure political tactic to try and influence this election,” Willems said. “The people should be concerned that the federal government is now filing criminal charges against their political opponents.  The voters of this county will not stand for this.”

Contributing: Megan Cassidy, The Arizona Republic. Follow Rebekah L. Sanders on Twitter: @RebekahLSanders