At least that’s how Nancy L. Cohen tells it in her new book ”Delirium: How the Sexual Counterrevolution Is Polarizing America,” published this month by Counterpoint Press in Berkeley, Calif.

Cohen’s theory goes like this: the sexual revolution gave us feminism and gay rights, which led to a shadow movement, a Republican backlash that was “ideologically powered, strategically organized, and well-financed.” This shadow movement has had staying power, she argues, influencing power politics for the past 40 years.

In her book, she tells the story of “how conflicts about sex, women’s rights and women’s roles, gay civil rights, and family drove Americans into irreconcilable warring camps.”

She blasts the Republican Party for its efforts to outlaw abortion, ban gay marriage and use legislatures and the courts to enforce traditional family values.

But she also goes after the Democrats — her tale, she writes, is not “about the Republican Party only. It turns out that the sexual counterrevolution has been a bipartisan affair.”

Cohen writes that as the sexual counterrevolution came onto the scene, the Democrats became embroiled in self-destructive infighting — a kind of civil war within the party.

George McGovern’s loss in the 1972 presidential election caused Democrats to blame the landslide on the radicalism of the candidate’s supporters: gays, feminists, multiculturalists, and elitist college students, a constituency that alienated Middle America.

Democrats are hesitant to embrace the party’s progressive legacy, Cohen writes, and have sought the middle ground out of political calculation, stalling progressive advances.

What it all adds up to is a kind of political delirium, Cohen believes. And while she notes that the sexual counterrevolution isn’t the only cause of America’s warring parties — race, war, money in politics and class all play supporting roles — it is “one of the few key dynamics driving contemporary American politics.”