In an ad backing Mitt Romney for president, a gold band on the main character’s left hand flashes before viewers as she laments a poor economic future for her two children should President Obama win re-election.

That hint to the character’s marital status reveals one of the subsets of voters that both Obama and Romney, his presumptive Republican opponent, are targeting in the 2012 campaign: married women with children.

They are a slice of the electorate that swing between the parties. They also are less likely than the broader female voting population to skew Democratic.

Obama won married mothers by 4 percentage points in 2008 compared to his 13-percentage-point margin among the gender as a whole, exit polls show.

“These women are the Republicans’ best shot,” especially in the swing states, said Ange-Marie Hancock, associate professor of political science and gender studies at the University of Southern California in Los Angeles.

In 1992, the so-called Year of the Woman, when female representation in Congress spiked, Democrat Bill Clinton won the White House with a plurality of women voters overall while losing the married-mother vote by 1 percentage point. Obama won’t win this year if that margin exceeds 5 percentage points, Hancock said.

To create a profile of that targeted female voter and learn how she’s changed in the past 20 years, Bloomberg compiled data from the Census Bureau, Bureau of Labor Statistics, the Pew Research Center and exit polls with analysis from Selzer & Co., a Des Moines, Iowa-based polling firm.

Compared with their 1992 counterparts, today’s married mothers are wealthier and more educated.

On average, they have annual household incomes of more than $70,000, a 14 percent increase from 1992, and 40 percent have earned at least a bachelor’s degree, compared with 22 percent two decades ago.

They work more hours and contribute more household income.

They are older when they walk down the aisle and when they first give birth. At both the workplace and in politics, more people in power look like them.

“It changes the way they view their role as mothers. It changes the way they relate to their husbands and other people,” said Christine Percheski, who assisted Bloomberg with the analysis and who teaches sociology at Northwestern University in Evanston, Ill.

“It changes what they need from government, and it changes what kinds of policies are important to them politically.”

Married mothers today are more likely to have lived on their own and worked more years prior to having children, and thus favor greater independence and identify less with traditional gender roles, she said.

Married mothers have become a more privileged, “select” group – half as likely to live in poverty or lack health insurance than women in general, she said.

“Because married mothers come from families with higher incomes, they need less of the social protections than some other women, and their financial interests and class interests lie more with the Republicans in terms of things like tax policy,” Percheski said.

They are also a more reliable voter then unmarried women, who studies have found tend to have a Democratic tilt.

Almost half of married mothers, 47 percent, went to the polls in 2010, compared with less than a third of their unmarried counterparts, 30 percent, said Page Gardner, president of the Women’s Voices Women Vote Action Fund.

As in 1992, voter surveys find economic issues identified as the top concerns during this campaign, and married mothers, who often control family finances, are no exception, a June 15-18 Bloomberg National Poll found.Married moms in the poll favor Obama over Romney, 50 percent to 46 percent, though 68 percent say the president hasn’t delivered the change he promised four years ago.