I noted earlier tonight, as the Michigan returns were coming in, that Mitt Romney’s lead in Michigan was due in large part to his strong margins in the five-county metro Detroit area, where Republican voters tend to be relatively upscale—not all rich people from Bloomfield Hills, Romney’s boyhood home, but from the relatively comfortable and competent suburbs in a metro area that has been troubled. The returns at this writing show that almost all of Romney’s statewide margin came from Oakland County, the relatively affluent suburban county just northwest of Detroit, which is the state’s second largest county and the one that cast the most votes in the Republican primary.

Four years ago Romney carried the five-county metro Detroit area 45%-27% over John McCain; this time he carried it 45%-32% against Rick Santorum. His metro Detroit margin enabled him four years ago to convert a narrow Outstate 35%-32% margin to a convincing 39%-30% victory. His metro Detroit margin this time was enough to overcome a 42%-38% Santorum margin Outstate.

Are there implications here for the general election. I have a hunch there are. Romney has shown in Michigan as elsewhere a capacity to win votes in affluent areas—which is exactly where (at least in the North) Republicans have been weak in presidential general elections over the last 20 years. Look at it this way: in 1988 George H. W. Bush carried the five-county metro Detroit area 50%-49%--a tiny margin, but one which enabled him, with a 56%-43% Outstate margin that was underwhelming in historic perspective, to carry Michigan. Similarly, the elder Bush, with big margins from affluent suburbanites, carried metro Boston, metro New York, metro Philadelphia, metro Cleveland and metro Chicago, which enabled him to win the electoral votes of New Jersey, Pennsylvania, Ohio, Michigan and Illinois.

In contrast, George W. Bush was able to carry only one of these states, Ohio, and was out of contention in 2004 as well as 2000 in Massachusetts, New York, New Jersey and Illinois. To focus on Michigan, the younger Bush carried Outstate Michigan 51%-46% in 2000 and 53%-46% in 2004, running just 5% and 3% in this region behind his father’s 1988 showing. That trend extrapolated statewide would have left him just missing carrying Michigan in 2000 and carrying it in 2004. But in 2000 George W. Bush lost the five-county metro Detroit area by 58%-40% and he lost it by an almost identical 58%-41% in 2004. Both times he lost the target state of Michigan.

A better showing in metro Detroit—even coming short of carrying the metro area, as the elder Bush did in 1988, and even short of improving on the younger Bush’s showings Outstate—would enable a nominated Mitt Romney to carry Michigan in 2012. And for similar reasons the electoral votes of Pennsylvania and New Jersey, might not be out of reach (New York, Massachusetts and Barack Obama’s Illinois would still, I think, be unavailable, but Ohio would be more available than in 2000 and 2004, when Bush carried it). I think the ingredients for this may be present.

Affluent suburban voters are not happy with the Obama economic polices and are facing a choice between a Democrat who wants to tax their marginal income at 44% and a Republican (whether it is Romney or Santorum) who wants to tax it at 28%. They are far less concerned than they used to be about the cultural issues which moved them to the left in the 1990s and kept them there up through and including 2008.

If they were repulsed by the Southern accents of Republican congressional leaders and the Texas twang of George W. Bush in those years, things are different now: Speaker John Boehner (not a major figure in the spotlight) is from the Midwest, and Romney speaks with a regional-neutral Northern accent, less distinctly Midwestern than that of some of us who grew up in Michigan, but nonetheless not at all threateningly Southern.

Affluent suburbanites are not a target group anyone has focused on much. But there are plenty of them and they tend to be in states with lots of electoral votes currently considered unavailable to Republicans. Mitt Romney’s showing in Michigan, on top of his proven appeal to this demographic—and particularly to affluent women—suggests they could make a difference in November 2012.