Democrats have long grumbled privately that Christopher J. Christie's tenure as U.S. attorney - marked by high-profile corruption prosecutions that made him one of New Jersey's most prominent Republicans - was tinged with political ambition.

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.

Two of them, Atlantic County Executive Dennis Levinson and former Republican National Committee Chairman Richard Bond, said in interviews Friday that they had not discussed politics with Christie.

Another, former Sussex County Republican chairman Rich Zeoli, said his one interaction with Christie while the latter was U.S. attorney was in his role as a congressional aide to U.S. Rep. Scott Garrett (R., N.J.).

"Chris was blind to what party the person was in," Bond said. "If they were corrupt, they were going down."

Democrats constituted the bulk of Christie's big corruption cases. They also hold the bulk of elected offices and power in the state.

Among Republicans he targeted were 11 officials in GOP-heavy Shore towns in a 2005 case.

But the latest criticisms have focused less on trials and more on political activity.

Asked for specific cases that Christie should not have prosecuted or should have handled differently, Corzine said Friday, "I think we'll speak more to those kinds of things as time goes on," adding that he would like to know more about the situation.

Though the Hatch Act bars covered federal employees from even initial campaign activity, whether a conversation with a political leader crosses the line depends on the circumstances, said Erica Hamrick, deputy chief of the U.S. Office of Special Counsel's Hatch Act Unit.

"There's no bright line. It's very fact-intensive," she said.

Daniel Richman, a Columbia University law professor who was a federal prosecutor in New York for 51/2 years, including a stint under Rudolph Giuliani, said politics and U.S. attorneys' offices were linked more than many people believe.

"These have always been political positions with some sort of political story attached to each office-holder's getting the job," he said.

Christie, he noted, had no prosecutorial experience before landing the New Jersey job but was a prominent fund-raiser for Bush, who later appointed him.

But Richman said there was a "long distance" between disagreement over cases a U.S. attorney should emphasize and allegations of ethical or legal violations.

"The best we can do is wonder and ask hard questions," he said. In a state known for graft, "the harder questions would have come had there not been any corruption pursued."

Mike Pinsky, a defense lawyer who cochairs the Camden County Bar Association Criminal Practice Committee, has battled federal prosecutors in court and said he often disagreed with U.S. attorneys' philosophies. But, he added, "I didn't see anything from Christie that . . . I could look upon as a politically motivated prosecution."

Senate President Richard J. Codey (D., Essex) has proposed legislation that would bar state prosecutors from seeking office for two years after leaving their posts.

"Given the power that prosecutors hold, it should be clear whether they are motivated by the sole desire to uphold the law or by future political aspirations," Codey said in a news release last week.

Such legislation would have slowed the political careers of many prosecutors. Gov. Rendell was once Philadelphia district attorney. Giuliani was a U.S. attorney in New York, and he drew criticism from some defense lawyers for what they said was grandstanding in that post.

Patrick L. Meehan, a former U.S. attorney in Pennsylvania, resigned ahead of considering a run for elected office. In May, he told a Pittsburgh TV station he wanted to avoid charges that his case against former State Sen. Vincent J. Fumo was fueled by politics.

Richman said he doubted there would be a sudden end to former prosecutors' seeking office. But he said when one runs, their body of work becomes a target.

"Somebody's decision [to run] may cast new light on, or shed ugly shadows on, the cases they brought before they left," Richman said. "I don't know if it's fair or not. It's certainly inevitable."