In 1960, it took an extraordinary candidate -- John F. Kennedy -- to surmount voter prejudice and become the first Catholic elected president of the United States.
In 2008, U.S. Sen. Joe Biden's Catholicism is touted as a solid political asset and one of the reasons he was chosen by Barack Obama to be his running mate on the Democratic ticket.
Political taboos that might have seemed intractable for time immemorial can crumble overnight. Americans had long assumed that a divorced candidate could never hope to win the presidency -- until Ronald Reagan made divorce a non-issue.
In his powerful and courageous speech on the opening night of this year's Democratic National Convention, U.S. Sen. Ted Kennedy urged Americans to "rise to our best ideals" in November. He offered Obama as the embodiment of that aspiration. "Barack Obama will close the book on the old politics of race and gender, of group against group, of straight against gay," Kennedy said.
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The old lion and liberal icon of the Democratic Party may have been reaching. He may be overestimating what both Obama and the American people are capable of.
But he nonetheless voiced a genuine hope felt not only among those assembled in the convention hall but also among many Americans of all political stripes that Obama's impending nomination represents an important threshold crossed. A black man could be elected president of this country. That no longer is a possibility that must be deferred to the distant future.
And that is true whether Obama wins or not. The taboo has crumbled.
Much the same could be said of Hillary Clinton's landmark primary campaign. While a woman has yet to ascend to the White House, Clinton's campaign has given that prospect a sense of inevitability it lacked before.
While the progress personified by the Obama and Clinton campaigns has been evident for some time, the convention itself has driven the theme home in a stirring way. African-Americans aren't just playing a subsidiary role in this election; they are at the center of it.
Yes, nominating conventions are carefully scripted, overly managed pageants designed to portray the candidate and his party in the most flattering light. But how the respective parties choose to do that can be revealing.
The aim of Monday's opening night ceremonies was to portray the Obamas as a wholesome, all-American family. The evening was capped by a polished speech by Michelle Obama and an appearance by her two daughters. Some commentators noted that this seemed to be the Huxtables, the idealized fictional family portrayed on "The Cosby Show," come to life.
To be sure, some stagecraft was involved. But the solid, loving family also seemed like the real thing.
And, as it was designed to do, this tableau posed the question: How could America be afraid of a family like that?
Good question, and, if Ted Kennedy is right, one we might never have to ask again.