April 23 (Bloomberg) -- This is expected to be a close U.S. presidential election and there’s a general consensus in both camps about who, to paraphrase former President George W. Bush, the “deciders” will be.

The swing groups are constituencies that went for Barack Obama in 2008 and voted Republican in the 2010 congressional elections, or voting blocs in which the premium is passion not preference.

-- Married women with children. There is a gender gap, and much of the focus now is on Mitt Romney and females. In 2008, Obama carried the women’s vote by 13 points. A more closely contested demographic, however, are married women with children, who are less Democratic than most other women. They account for about 15 percent of the electorate and went for Obama 51 percent to 47 percent four years ago, but swung to Republicans in the midterm elections.

“This is a group that Romney ought to carry,” says Whit Ayres, a Republican poll taker.

The issue of not getting the economy on track is of particular importance to married women. Anecdotal evidence suggests that some issues such as abortion and contraception don’t resonate as much. One concern they do have is education; this debate hasn’t yet begun in the campaign and is an area where the Obama forces say they have the advantage.

-- Suburban independents: This group made up about 12 percent of the electorate in 2008 and went for Obama by 7 percentage points, about the same proportion as his overall margin of victory. In the 2010 House races, Republicans carried these suburbanites by almost 25 points, a huge turnaround.

These voters vary slightly from the general electorate in several different ways: They are a little bit more male, more middle-upper income, more college-educated, more likely to be investors and slightly more middle-aged.

-- Catholics who aren’t regular churchgoers: Catholics, who account for a little more than a quarter of the electorate, are closely divided between those who regularly attend church and those who don’t. The most observant tend to be the most Republican and most responsive to their bishops’ criticisms of the president.

“John McCain carried these active Catholics last time, though not as much as George W. Bush did in 2004,” says Steven Wagner, who runs an opinion-research company and provided counsel on the Catholic vote to Karl Rove, Bush’s political adviser. “If McCain had matched Bush with active Catholics, it would have made a difference in several states.”

There’s a much smaller group of Latino and African-American Catholics who are expected to vote decisively Democratic. The swing group is comprised of white Catholics who aren’t regular churchgoers and not as in tune with the religious leadership. Their vote is likely to be affected by whether they are swayed by the criticism that Obama’s health-care policies have infringed upon religious liberties, as the bishops charge, or whether they believe Republicans are trying to limit the use of contraceptives (which most Catholics use).

In 2008, non-churchgoing Catholics went about 58 percent to 40 percent for the Democratic nominee; about the same margin voted Republican in the House races two years later.

-- Evangelicals: White evangelicals comprise about a quarter of the electorate and overwhelmingly vote Republican. The turnout and energy of this constituency this year are the unresolved questions. For Republicans, the model is the 2004 Bush re-election campaign, which benefitted from a sizable evangelical turnout.

Michael Lindsay, president of Gordon College, a Christian school near Boston, who has studied the evangelical vote, believes this year’s Republican nominee can do better than McCain -- who he says was “religiously unmusical.” His advice: bring in to the inner circle a few strategists with credibility in the evangelical community. One of the few current top Romney advisers who meets that criteria is former Minnesota Governor Tim Pawlenty, though he isn’t a Romney intimate.

Gordon says the candidate must select a running mate who energizes evangelicals. He also must “at some stage, give a talk about relevance of his faith to his positions and policies.”

Romney is working this territory hard; next month, he will deliver the commencement address at Liberty University, the fundamentalist school of the late televangelist Jerry Falwell.

-- Latinos: This is the fastest-growing voting bloc. Four years ago, they probably comprised 8 percent to 9 percent of the electorate and went for Obama by more than 2 to 1.

Romney is considerably less popular with Hispanics than McCain was four years ago. The presumptive 2012 Republican nominee adopted a hard line on immigration during the primaries, suggesting his opponents, Texas Governor Rick Perry and former House Speaker Newt Gingrich, were soft on the issue.

Romney and the Republican National Committee plan a Latino outreach effort and the candidate is trying to recalibrate some of his hard-line positions. Still, Republicans privately acknowledge that this is an uphill slog as he has created enmity in the Hispanic community. A NBC/Wall Street Journal poll last week showed Obama winning this vote, 69 percent to 22 percent.

As with evangelicals, the question with this group is intensity. Although the Hispanic voting-age population is more than 10 percent larger than it was in 2008, registration was down by more than 500,000 in 2010. Democrats argue that the high stakes of the presidential election and the hostility to Romney could produce a surge of Latino votes approximating the increase in population.

Their impact is pervasive in states with heavy Hispanic populations such as New Mexico, Colorado and Florida. In Virginia, Hispanics comprised an estimated 4 percent of the vote in 2008. Yet, in what may be the most closely contested state in the country, another percentage point, or 40,000 more Latino voters might well enable Obama to keep Virginia in the blue column.

(Albert R. Hunt is Washington editor at Bloomberg News. The opinions expressed are his own.)

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To contact the writer of this column: Albert Hunt in Washington at ahunt1@bloomberg.net

To contact the editor responsible for this column: Max Berley at mberley@bloomberg.net.