"It's a tacit admission that this is the guy they're going to be working with for the next few years, so they might as well make nice now," said Patrick Murray, a Monmouth University political scientist.
While Christie has received reelection endorsements from a handful of Democratic elected officials and unions, the most recent events are technically nonpolitical, meaning they're paid for by tax money rather than campaign funds and there are no endorsements.
And they have been on such issues as drug policy, education, and urban policing, where Christie and some of his political adversaries do agree.
"This is all fairly run-of-the-mill, standard stuff," said David Turner, the spokesman for Christie's likely Democratic opponent in his reelection bid this November, State Sen. Barbara Buono. "Just because he's standing with Dems doesn't mean he's not out of touch with Dems and most of the state."
Turner said that on issues such as job creation, taxes on high earners, tax credits for the working poor, and gay marriage, most New Jersey voters are closer to Buono than Christie.
Christie said there's more to it than that.
After meeting with women incarcerated at the Hudson County Jail, where McGreevey now works as a spiritual counselor, Christie spoke about his relationship with McGreevey, a Democrat who dramatically left office in 2004 after announcing he was gay and had an affair with a male staff member.
"People think politics and personal relationships are contained in absolutes, so if you disagree on one thing you can't possibly be friends," Christie said. "Jim and I have certain philosophical disagreements, and we live with that. That's what our country is about."
McGreevey said he has the "greatest personal respect and admiration" for Christie and appreciates that he is a Republican willing to advocate drug treatment rather than prison for some drug offenders.
Would he go as far as endorsing Christie?
"I'm out of politics," McGreevey said.
Since he has been in office, Christie has tried to contrast himself with the ways of a gridlocked Washington where opposing parties have a tough time getting much done.
With both chambers of the Legislature controlled by Democrats, all laws Christie has signed - a property-tax cap, an overhaul of pension and health care rules for public workers, a change in the teacher-tenure system among them - have had Democratic support.
His appearances with Democrats seem to have ramped up in this election year, perhaps because this is a state where there are 700,000 more registered Democrats than Republicans and where Democrats consistently dominate in elections for federal seats.
"It makes sense to be the conservative Republican who can work well with lots of different kinds of Democrats," said Rider University political scientist Ben Dworkin.
While incumbent governors in an election year often turn up in what could be hostile political territory, Murray said he has noticed that the Democrats appearing with him have gone far beyond just politely thanking him for being there.
"The Democrats are embracing him so heartily," Murray said.
Camden Mayor Dana L. Redd, who is also vice chairwoman of the state Democratic committee, praised Christie last week as a partner in trying to help revive the city.
One of the biggest Democratic power brokers, Essex County Executive Joseph N. DiVincenzo, appeared with Christie this week at a groundbreaking for a new building at a Newark technical school.
Buono should not worry that Christie is cavorting with Democrats but should focus on trying to get her party's political bosses to commit to helping her campaign, said Ingrid Reed, a political analyst who is retired from Rutgers University's Eagleton Institute of Politics. Buono is in danger of not raising enough in campaign contributions to get the maximum match under a public campaign finance law.