Our national immigration policy is broken and Congress has given up trying to fix it. Illegal immigrants now number about 12 million, and more arrive daily. In some parts of the country, they are straining the capacities of schools and hospitals. Some economists believe that massive immigration is driving down the wages of low-income citizens. On the other hand, many immigrants are paying money into our Social Security system, though they may never receive benefits. And others have been detained and languish in federal prisons.

Starting in 2005, prominent Democratic and Republican senators, supported by the president, worked hard to reform our national immigration policy. But by June 2007 these efforts had failed, and Senate leaders stopped pushing for reform.

Why have these efforts failed? Because we lack a national consensus on what immigration policy is supposed to accomplish — we differ among ourselves about basic objectives. Our differences about objectives, in turn, reflect fundamental differences in values and in our views of America’s historic mission regarding immigration.

Some Americans would like to stop immigration completely, or at least drastically curtail it. While some supporters of this view may be racists, others are genuinely concerned that we simply cannot integrate the huge flow of immigrants, many brought up in other cultures and unable to speak English.

In radical opposition to this view are people who believe that humanitarian goals should be dominant. They believe we became a great nation partly by welcoming millions of immigrants — most not English speakers — fleeing poverty or oppression. Above all, we would violate basic American values if we try to deport 12 million people.

Still others argue that U.S. technological leadership and economic growth should be our dominant objectives. We should welcome with open arms those immigrants — scientists, engineers, software developers — who can develop advanced technologies; but we should restrict entry of all others. These people believe that preserving America’s continued technological leadership is critical to our future.

Some business leaders want permissive immigration policies. A plentiful supply of low-wage workers helps our companies remain profitable, ensuring they can survive without moving overseas. Some of these people may be focused only on their own companies’ profits, but many honestly believe that vigorous pro-business policies explain our past prosperity and can ensure future economic success.

Finally, some believe that our immigration policy must, above all, protect the living standards of low-income Americans. As noted, some economic research — though not all — finds that immigration drives down low-income Americans’ wages. People with this belief are committed to the traditional American value of helping fellow citizens in need.

So Congress’ failure to reform our broken immigration system reflects, at the deepest level, profound disagreement among Americans about the values embedded in our historic mission. The apparent failure of Congress actually springs from this disagreement.

What will happen next? In January, the new president and the new Congress will be confronted afresh by the reality that our immigration policy is broken. Three outcomes are possible.

First, Congress might remain deadlocked; by default, our present failed policy would continue.

Alternatively, congressional leaders might manage, despite our underlying value differences, to cobble together a hodgepodge of provisions that could muster a majority in Congress. But such hodgepodge legislation surely would embody internal contradictions, leading in the end to an unworkable policy — perhaps no better than our current policy.

Finally, the new president might try to identify elements of common ground underlying our differing values and then draw on these elements to build a consensus around new and better policies. A new approach surely would include a humanitarian, or at least a pragmatic, opposition to deporting 12 million people. It also would include measures to reduce illegal immigration, to ease the heavy demands on overburdened schools and hospitals.

We need a president willing to tackle the tough job of searching for this common ground and then selling better policies to the public. At the moment, neither Barack Obama nor John McCain is addressing immigration issues and neither seems willing to accept the challenge of fixing our broken policy.

Edwin Dean, an economist and seasonal resident of Vinalhaven, writes monthly about economic issues.