Revelations last week that Christie twice spoke about a potential run for N.J. governor with Karl Rove, a top strategist to former President George W. Bush, brought those criticisms public.

"It's now clear that Christie was laying the groundwork for his gubernatorial campaign while he was serving in the U.S. Attorney's Office," said Gov. Corzine's running mate, Loretta Weinberg.

Federal employees such as U.S. attorneys are barred from engaging even in preliminary campaign activity under the Hatch Act, a 1939 law enacted in part to ensure that government carries out its functions equally. Decisions about whom to prosecute should be free of politics, experts on legal ethics say.

Christie's camp has dismissed suggestions that the GOP challenger to Corzine crossed the line.

"Jon Corzine and his campaign are doing what they do best: making false accusations to distract from the real issues," Christie spokeswoman Maria Comella said.

She described the talks with Rove as informal.

Rove, facing questions from Congress about his role in the firings of some U.S. attorneys, testified July 7 that his conversations with Christie were unrelated to the Republican's work as U.S. attorney.

In his testimony, released last week, Rove told congressional investigators that he spoke with Christie "a couple of times . . . regarding his interest in running for governor" and that Christie asked about "good people that knew about running for governor that he could talk to."

Rove said "perhaps" one such talk happened while he was at the White House, which means Christie would have still been U.S. attorney. Rove left the White House in August 2007. Christie resigned in December and announced his candidacy in January.

"At best, there's an appearance problem," Corzine said Friday. "The administration of justice shouldn't be compromised with politics. Whether one crossed the line on the Hatch Act or whether that's an appearance issue, I don't think that's a healthy position to be in."

Rutgers University political scientist Ross Baker said he expected Corzine to rally supporters by tying his opponent to Rove, a "figure of great loathing" among Democrats.

It's unclear when Rove and Christie had their second conversation. As of Friday, Christie had not made himself available to the media to discuss Rove's comments. His campaign would not provide details of when the conversations happened or who initiated them.

U.S. attorneys are appointed by the president, but their cases are supposed to be free from personal political interests, said William Jeffress, a Washington lawyer who has chaired the American Bar Association's Criminal Justice Standards Committee.

Christie points out that corruption cases he prosecuted - more than 100, targeting Democrats and Republicans - never resulted in an acquittal.

Democrats, however, chafed as major indictments drew hordes of media to Christie's bravado-filled news conferences and toppled prominent party figures, including former State Sen. Wayne Bryant of Camden County.

Some indictments, they complained, read like crime novels and leaks seemed too conveniently timed.

Two months before Election Day 2006, for example, word got out that Sen. Robert Menendez (D., N.J.) was the subject of an investigation. The story became the backbone of the Republican campaign against him, but Menendez was never charged.

From the start of this general election campaign, Corzine's team has tried to tarnish Christie's prosecutorial record.

Democrats attacked him for awarding a contract worth up to $52 million to the firm of his onetime boss, former U.S. Attorney General John Ashcroft. After the news about Rove broke, they referred to media reports, some dating to 2004, about top Republicans with whom Christie met while he was U.S. attorney.