Running for president was always an unlikely next step for Mayor Bloomberg. Running for governor is likely, and becoming more so.

Mr. Bloomberg and Governor Spitzer don’t get along very well. They understand their mutual need to accomplish individual goals while in office, but as individuals they don’t have much in common beyond liking a coffee shop situated near their Upper East Side residences.

Don’t expect to hear much talk from the Bloomberg camp about running for governor. The nonstop talk about running for president was a requirement to make Mr. Bloomberg a viable candidate. The concept of Mr. Bloomberg entering the presidential race seemed absurd when the rumors first began two years ago. A coordinated pre-campaign was required to make plausible a campaign that now is not happening. Convincing voters and opinion makers that Mr. Bloomberg is a reasonable gubernatorial candidate with a reasonable chance of winning isn’t an issue. Polls at this early date — nearly three years before the election — even show Mr. Bloomberg ahead of Mr. Spitzer. So in terms of running for governor, talk would only hurt Mr. Bloomberg’s chances, as it could cause trouble with the current governor.

The mayor does not want any trouble with the governor, and vice versa. From Mr. Bloomberg’s perspective, Albany has a say in almost every big idea any mayor wants to pursue. From Mr. Spitzer’s perspective, last summer’s Troopergate troubles make it imperative to avoid any new high-profile enemies.

Political necessity has kept the tensions between the mayor and the governor largely under the radar, allowing them to develop a very productive working relationship. Mr. Bloomberg lent Mr. Spitzer some much-needed political capital by appearing with the governor during some of the most difficult weeks last summer. Mr. Spitzer spoke glowingly of Mr. Bloomberg during the State of the State address in January.

On the policy front, Mr. Spitzer is offering unwavering support for Mr. Bloomberg’s most immediate priority: congestion pricing. Mr. Spitzer is putting heavy pressure on fellow Democrats in the Legislature to approve a congestion pricing plan, perhaps as part of a deal for a pay raise. Lawmakers realize the oddity that their best hope for their first pay raise since 1999 could hinge on making Mr. Spitzer happy so he can make Mr. Bloomberg happy.

Messrs. Bloomberg and Spitzer have shown a knack for helping each other out, but the tension between them does bubble when they don’t agree on policy matters. When Mr. Bloomberg criticized Mr. Spitzer’s now aborted plan to offer drivers’ licenses to illegal immigrants, Mr. Spitzer declared: “He is wrong at every level: Dead wrong, factually wrong, legally wrong, morally wrong, ethically wrong.”

Smack in the middle of an ethics scandal, Mr. Spitzer challenged Mr. Bloomberg’s thus far unimpeachable ethics — even while Mr. Bloomberg was offering the governor much-needed political support. Whether that moment was a cause or a symptom of friction is less significant than what the moment disclosed about the tenuousness of their relationship.

There have been other hints recently that their public support for each other masks fundamentally different views of how to govern. Mr. Bloomberg threatened to shutter off-track betting as Mr. Spitzer tried to boost the horse racing business. Mr. Spitzer threatened to sell land crucial to expanding the Jacob K. Javits Convention Center as Mr. Bloomberg pushed for a bigger convention center.

At every turn, Mr. Bloomberg finds himself appealing to Albany for help. The mayor needed to win Albany’s approval to take control of the city’s school system, failed to win Albany’s backing for a football stadium on Manhattan’s West Side, and needs to win over Albany on congestion pricing. Becoming governor after he stops being mayor would enable Mr. Bloomberg to decide rather than having to ask.

The Republican and Independence parties would welcome Mr. Bloomberg’s entry into the race, and so far the mayor’s popularity seems to be holding strong. He’d immediately be a strong contender in a race against Mr. Spitzer — even before factoring in his unlimited supply of campaign funds and recent $500,000 contribution to the same Republican party he recently (and perhaps temporarily) quit.

The only certainty in Mr. Bloomberg’s future is that he must leave City Hall on December 31 of next year. What’s next hinges of a variety of factors, beginning with what he decides to do with Bloomberg LP.

Various tax and estate planning implications suggest Mr. Bloomberg will want to sell his private company relatively soon — this is likely why Mr. Bloomberg recently installed a former deputy mayor with a deal making background, Dan Doctoroff, at the top of the company. Selling the company would net Mr. Bloomberg billions of dollars to ramp up the charitable foundation he’s often talked about.

There’s no sign Mr. Bloomberg wants to give up the instruments or influences of political power. If polls show on January 1, 2010, what they show now, it’s as hard to envision Mr. Bloomberg not running for governor as it was to envision him actually running for president.

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