There is no assurance last week's healthcare overhaul will expand the Democratic coalition despite representing the most sweeping social legislation since the 1960s, based on a RealClearPolitics analysis. Even under a best-case scenario for liberals, in the long term, the law will likely only bolster the Democratic coalition on the margins.

The uninsured have a low voter registration rate. They already lean heavily Democratic. The legislation will only aid a small portion of swing voters. And there is also the much-discussed matter of timing. Most of the 32 million Americans expected to gain health insurance coverage will not do so until 2014.

Democrats still have reason for restrained optimism. The healthcare overhaul could, however marginally, help expand the Democratic coalition in the next decade. But unknowns temper even this ideal Democratic scenario. What other legislation could have been, like historic jobs bills, if not for the yearlong healthcare fight? How would that legislation have impacted the coalition? And how many swing voters have been lost over this legislative fight?

About six in 10 uninsured adults lean or already indentify as Democrats, based on Pew Research Center polling. Little more than a fifth of the uninsured indentify or lean Republican. And roughly another fifth of the uninsured are true independents

But only a slim majority of uninsured adults are registered to vote, compared to more than eight in 10 of those with health insurance. That means the healthcare overhaul's target audience, about half of uninsured independents, totals 3.7 million, or nearly 3 percent of the 2008 electorate.

Working class whites constitute the largest share of this potential swing vote. They make up about 40 percent of the roughly 38 million adults without health insurance, based on a Kaiser Family Foundation study of census data. But nearly all will qualify for coverage under the law. Still, even their numbers are tempered by current political allegiance.

A slim majority of uninsured working class whites already indentify or lean Democratic, far above the Democratic allegiance of their insured counterparts. That leaves only 14 percent who are true independents. At most, Democrats have an audience of about 2.2 million working class whites to pitch the merits of their reform. And as with any bloc, a smaller portion will actually vote.

College-educated whites, meanwhile, constitute only 7 percent of the uninsured. About a fifth of them are likely to be true independents.

Minorities make up a slim majority of Americans without health insurance. But the legislation has even less potential, when compared to whites, to win new Democratic voters among them.

Most Americans of color, particularly within the working class, already vote Democratic. Many minorities also have a far lower qualification rate for coverage under the law. The Pew Hispanic Center estimates that about 60 percent of uninsured Latino adults and 35 percent of uninsured Asian adults are ineligible for coverage. They are either illegal immigrants or have been legal residents for less than five years. By comparison, 96 percent of all other races who are uninsured, mainly whites and blacks, qualify for coverage.

Hispanics constitute 31 percent all uninsured adults, 11.5 million in total. But with only a minority of them eligible for coverage, and with lower turn out rates than even working class whites, Democrats have little reason to think this legislation will greatly influence the key Latino swing vote.

This legislation will influence the black vote still less. About 15 percent of the uninsured are black. But Democrats already win near-unanimous black support.

Democrats' best hope to court the uninsured will be after 2014, when the law is expected to fully take shape. Today, more men than women are uninsured. Nearly nine in 10 of the uninsured are working class. An equal share is under age 55. And almost four in 10 are under age 30, according to Kaiser's research.

The long-range political impact of the law is complicated by age as well. Some children covered by the overhaul will be voting adults by 2014. But some portion of today's uninsured will also reach Social Security age at that point and they would have earned coverage regardless.

Not since Democrats pushed programs from the New Deal to the GI Bill has far-reaching social reform clearly transformed the electorate to the political left's advantage. In the 1960s, civil rights reform cemented Democrats black support for generations but it cost them most Deep South whites.

In the end, predicting the long-range political impact of healthcare reform is an inexact science. One major unknown variable is the economy.

For every voter who said healthcare is a top issue in the past year, at least five voters said the economy and jobs. And at least two-thirds of the Great Recession's job losses are blue collar, the same bloc most likely to be helped by the healthcare legislation. Many of these voters could come to view Obama's priorities in conflicting terms.

Today, polls show that more Americans disapprove than approve of the healthcare law. And only one third of white women and men approve, according to a recent Quinnipiac poll. Democrats believe the legislation will become more popular in the years to come. But the opposite could also prove true.

By 1966, according to the Gallup Poll, less than half of Americans supported Lyndon Johnson's anti-poverty program. It was a far stronger economy then. The programs were less divisive than today's healthcare legislation. They significantly reduced black and white poverty. But on balance, the Great Society did not clearly strengthen the Democratic coalition in the long run.