Baby boomers who came of age during the social and political upheavals of the 1960s and 1970s tended to call themselves Democrats, and as time passed, that identification strengthened.

In 1969, far more in the 18- to 29-year-old age cohort — the front end of the baby boom — called themselves Democrats (35 percent) than Republicans (21 percent). A decade later, when they were 28 to 39 years old, their identification with the Democratic Party over the GOP was even stronger (45 percent to 19 percent in Gallup’s surveys).

But starting in the 1980s, attitudes of the baby boomers began changing. Polls found them becoming more family oriented and, over time, more conservative. If this transformation continues, leading more of them to embrace the GOP, it could affect the 2012 election.

Although characterized as rebellious, the vast majority of boomers were not actually radical during the 1960s and ’70s. In fact, it was older, less-educated Americans who first called our involvement in Vietnam a mistake, not the younger, college-educated “antiwar generation.” Young people were, initially at least, more supportive of going to war in Vietnam than their elders.

When the ’60s generation was asked in the 1980s to look back to its supposedly tumultuous youth, the recollections were more tame than many had expected.

In a 1986 poll for Time magazine, only a third of the generation said they had favored the social protests and demonstrations of the 1960s and ’70s, and only a quarter said they took part in them.

A mere 8 percent of respondents said they used marijuana regularly during the 1960s and ’70s, although 26 percent acknowledged occasional use. And just 18 percent of those surveyed in a poll done for Rolling Stone magazine in 1987 said they had pursued a countercultural lifestyle in the late ’60s.

Baby boomers were, however, less conventionally religious than their parents, and more liberal on racial issues, homosexuality and women’s roles.

Some three-quarters of those polled by Rolling Stone said their parents’ generation put more emphasis on organized religion than they did, had more respect for authority and believed more in tried-and-true methods.

The spirit of openness of the counterculture left a deep impression on them. In the Rolling Stone poll, 83 percent stated that their generation’s willingness to be more open and share personal feelings was a change for the better from their parents’ generation.

But the natural conservatizing effects of aging were also becoming evident in these 1980s polls. The passions of youth had been tempered by the practical reality of marriages, children and mortgages. Nearly 7 in 10 in the Rolling Stone poll said they were more family oriented than they thought they would be.

When asked about changes from their parents’ generation, 59 percent said more-permissive attitudes about sex were a change for the worse (31 percent thought it was for the better), 67 percent said more single parenthood was a change for the worse, and 72 percent said they thought less religious training for children was a change for the worse.

Ideological beliefs moved too. In the 1986 Time poll, 64 percent of the baby boomers polled said they had become more conservative since the 1960s. When asked about their ideological identification, 31 percent said they had been liberal in the 1960s and ’70s, but only 21 percent described themselves that way in 1986. The number identifying as conservative rose from 28 percent to 41 percent.

The ideological reorientation of early boomers that began in the 1980s has continued. Two of the country’s best long-running surveys show how those born between 1943 and 1958, the so-called near-olds at the front of the baby boom, have changed. In the 1972 American National Election Study survey, 30 percent of today’s near-olds called themselves liberals. In 2008, 12 percent did.

The proportion calling themselves conservative rose from 21 percent to 46 percent. In 1972, 51 percent of eligible voters in the early baby boom cohort called themselves Democrats and 29 percent Republicans. In 2008, 45 percent said they were Democrats and 48 percent said they were Republicans.

The National Opinion Research Center’s data also show a substantial increase (18 points) between 1974 and 2010 in conservative identification for the near-old cohort and a smaller movement in the GOP’s direction. Those born between 1927 and 1942 changed far less in both surveys.

The importance of the ’60s generation is magnified by its demographic weight. The near-olds vote in much higher numbers than some other groups.

Census data from 2008 showed that 49 percent of the eligible voting-age population between the ages 18 and 24 turned out to vote, while 72 percent of the larger 55-to-63 group said they voted. The combined electoral heft of the near- and new-olds could dramatically alter the political landscape.

Today both groups are deeply dissatisfied with President Obama. About 43 percent of those ages 50 to 64, and just 33 percent of those over 65, approved of Obama’s job performance, according to an August Gallup poll.

A new poll from the Pew Research Center shows a fairly even division among registered voters in the 50- to 64-year-old baby boom group about re-electing Obama. Thirty-eight percent told the pollsters they would prefer to see him re-elected while 42 percent would like to see a Republican candidate win.

In 2008, the near-olds divided their votes between Obama and Sen. John McCain, making them more Republican than the population as a whole.

Formative political experiences anchored the ’60s generation in the Democratic Party, and they have not so far embraced the Republican Party as much as might be expected from their ideological transformation.

It isn’t clear who they will favor in 2012, but they are more open now to hearing a GOP message than they were in their early years. Both parties ignore that evolution at their peril.