Congestion pricing is beginning to feel a bit like Dr. Evil’s “laser” in “Austin Powers” — we know it’s there, but we’re not exactly sure what it does.

The good news for Mayor Bloomberg is that he’s likely to win some sort of “congestion pricing” plan by the spring now that the Assembly speaker, Sheldon Silver, is on board with developing a plan to reduce Manhattan traffic by charging a fee to drivers. This is noteworthy because Mr. Silver has played the recurring role of obstructionist to some of Mr. Bloomberg’s boldest ideas during the past six years.

We won’t know what congestion pricing really means until much closer to the March 31 deadline for final approval from the City Council and state Legislature. We do know there’s no chance the ultimate agreement will look much like the original proposal for using hundreds of cameras to charge $8 a car for all cars below 86th Street — with a rebate for any tolls drivers paid to enter Manhattan.

That initial idea actually gives a free ride to drivers who enter Manhattan via the Triborough Bridge, Midtown Tunnel or Battery Tunnel (already exactly $8 round-trip with E-Z Pass) and a big discount to New Jersey drivers (who pay $5 round-trip) with E-Z Pass. The big losers under the original plan are those drivers from Westchester, Brooklyn and Queens who currently travel free on bridges.

The final deal will likely put a bigger burden on New Jersey drivers while adding some fee for drivers who currently pay nothing to enter Manhattan. The city council is the biggest obstacle, because 30 of the 51 members hail from Brooklyn and Queens. They understand clearly how the initial “congestion pricing” plan targets their constituents.

“Congestion pricing could be three blocks with some cameras around them,” quipped one person involved in the process who doesn’t particularly like any of the ideas currently being floated. “But there will be something the mayor can call ‘congestion pricing’ by the time this is done.”

Mr. Bloomberg’s determination to do something about the unacceptable traffic that frustrates everyone trying to move around Manhattan is benefiting from a combination of technology and timing. Cameras can now easily read license plates to ensure drivers pay up, far different from just a few years ago when actual toll booths were needed. And there are genuine environmental benefits, making the general concept difficult to oppose in the year that green has gone mainstream.

Presuming some deal does win support from the City Council, congestion pricing should be home free when Albany lawmakers and the governor are asked for final approval.

The Republican-led state Senate isn’t an obstacle because the majority leader, Joseph Bruno, is in active war with Governor Spitzer and is forever at odds with Mr. Silver — making Mr. Bloomberg a critical ally. Mr. Spitzer is so grateful for the mayor’s recent support that a veto on a topic so important to Mr. Bloomberg is unimaginable. Mr. Silver is signaling he’ll let the Assembly go along with whatever his fellow Democrats who control the City Council decide.

Mr. Silver’s decision to offer an assist on the traffic plan marks a significant shift in his dealings with mayor. Mr. Silver infuriated the mayor in 2005 by blocking his dream of a West Side stadium for the Jets, thus preventing an Olympics in New York and with it the biggest physical legacy Mr. Bloomberg had hoped to leave. And Mr. Silver just a few months ago put the brakes on a key part of an innovative and widely applauded new trash plan.

Mr. Bloomberg’s tremendous success and popularity stem largely from how delicately he’s woven together two distinct yet substantial sources of clout: The governmental authority that empowers any mayor, and the personal influence that empowers any philanthropist promising to give away billions of dollars.

Mr. Silver has been largely immune from that intoxicating brew in part because he has so much power himself. In a twist that surely maddens the mayor, Mr. Silver wields tremendous control over Mr. Bloomberg’s ability to govern. Albany must sign off on a wide spectrum of city initiatives, including the annual $400 rebate checks for homeowners that are one of Mr. Bloomberg’s signature initiatives.

In congestion pricing, Mr. Bloomberg seems finally to have stumbled upon a bold idea Mr. Silver will embrace. As a shrewd negotiator who’s mastered the patience of waiting until the last minute, Mr. Silver will surely extract some concessions — such as more cops on the street to prevent double parking and crack down on drivers who created gridlock by blocking the box.

But those conversations will be the side-show. After years of being the chief agitator of the mayor’s agita, Mr. Silver will finally utter a word that has proven elusive, is really very simple and, to Mr. Bloomberg, could even sound magical… “Yes.”

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