By Noah Feldman

With his announcement that the United States will open negotiations to normalize relations with Cuba, President Obama is trying to break the hold of the Cuba lobby. In historical terms, that's a remarkable undertaking.

For decades, U.S. policy toward Cuba has been guided by the smart, effective lobbying of a relatively small group of interested Cuban Americans, mostly in Miami. The lobby's success has reflected a deep truth of American politics: Where there's a concentrated interest on one side of an issue and only a diffuse interest on the other, the concentrated interest wins.

Will it work? If so, why now? And what are the implications for other concentrated lobbying groups, such as the National Rifle Association and the pro-Israel lobby, which have themselves succeeded by following a version of the approach that the Cuba lobby pioneered?

Begin with an incontrovertible fact: Obama's opening to Raul Castro's regime is precisely what the Cuba lobby has long feared and opposed. Its two leading voices in the Senate, New Jersey Democrat Robert Menendez and Florida Republican Marco Rubio, immediately condemned Obama's apparent swap of three convicted Cuban spies for American Alan Gross and another unnamed American held on espionage charges in Cuba. Rubio told the Associated Press that Obama was playing into the Castros' hands, "providing the economic lift that the Castro regime needs to become permanent fixtures in Cuba for generations to come."

Since the end of the Cold War, independent foreign policy experts have argued that U.S. interests would be served by opening relations with Cuba. Once communism no longer needed to be contained or combated on a global scale, the reasoning runs, the United States would gain in trade with Cuba. Indeed, the infusion of capital and tourism into Cuba that would come with an end to U.S. sanctions would further weaken the socialism that exists there.

Yet despite the broad consensus in foreign policy circles, U.S. policy until now hasn't really changed - and the reason has been the effectiveness of the anti-Castro lobby. The explanation isn't that there are so many Cuban Americans: There are about two million, of whom some 70 percent live in Florida. And not all Cuban Americans support a strong policy of nonengagement with the island.

The reason for the lobby's success has been the discipline with which it pursued its agenda. A handful of politicians receive extensive support from the lobby, and their views, unsurprisingly, correspond closely to those of the Cuban Americans who support them. Other politicians may receive occasional support, but the lobby is not focused on them. The key to the operation is that on the other side, there is no concentrated interest group advocating for the normalization of relations with Cuba. For example, big agriculture corporations like Archer Daniels Midland would benefit from opening up trade, but it is a global company with lots of fish to fry.

If this model of advocacy sounds familiar, it should. The same basic structure explains the success of the NRA and the pro-Israel lobby exemplified by the American Israel Public Affairs Committee. None of these organizations is breaking the rules. To the contrary, their success reflects the structure of U.S. politics. Those who support gun rights care deeply about the issue: They're the essence of a concentrated lobby. Those who would regulate guns are almost by definition more diffuse. They might be motivated after an event like the Newtown, Conn., shooting, but over time, diffuse interests return to their natural state of diffusion.

The Israel lobby succeeds not primarily because of its financial capacity or disproportionate cultural influence, but because there is no concentrated pro-Palestinian lobby. Polls suggest that many Americans favor the idea of evenhandedness between Israelis and Palestinians. But any such impulse is highly diffuse, whereas the small number of Jewish Americans who pay the most attention to promoting Israel's interests as they see them are highly focused and concentrated.

Why does Obama think he can beat the Cuba lobby now?

The accidental political configuration of the moment provides the best explanation. His executive action on immigration reform has given the president - and probably the Democrats - a big boost among Latinos. He won't be running for reelection, and House Democrats will be vulnerable for another two years. As for Hillary Clinton, if she faces Jeb Bush in the 2016 campaign, she will probably have to find a path to victory that doesn't involve winning Florida, Bush's home state. This frees up Obama and the Democrats to take a crack at the Cuba lobby.

But the game won't be over with the opening of negotiations, which the president can do on his own. Restoring full diplomatic relations and ending the embargo will require Congress' assent. Here the lobby can be expected to go into full concentrated opposition mode - and it has some chance of success.

What Obama must be hoping is that groups with a passing interest in the opening to Cuba will get on the bandwagon just long enough to counterbalance the power of the lobby and get the necessary legislation passed. Big ag will still have a diffuse interest - but perhaps the vision of money on the table in the near future will motivate sufficient support.

The risk that Obama carries isn't totally unfamiliar to him. After all, he tried to take on the NRA by pushing gun control after Newtown. When he lost, the political cost to him was much less than the cost of doing nothing. On Israel, Obama has trod much more carefully, limiting himself to the message that he thinks West Bank settlements - and Prime Minister Benjamin Netanyahu - are obstacles to peace. Many pro-Israel lobbying groups detest him for it, but they haven't gone to war against him.

With the end of his presidency in view, Obama has to take risks if he wants to score some legacy points. His gamble on Cuba may not be fully realized. But the results will have implications for the structure of American interest group politics more broadly.

Noah Feldman is a Bloomberg View columnist. nfeldman7@bloomberg.net