Who’s mainstream? Whose mainstream?

That’s not just a word puzzle — those are two questions that sprung to my mind as I watched Senate Judiciary Committee Republicans excoriate Supreme Court nominee Elena Kagan for, among other things, growing up on the Upper West Side of Manhattan.

As soon as I learned that Kagan grew up there, when President Barack Obama nominated her to the high court, I wondered whether I might have met her as a kid. I, too, grew up on the Upper West Side, and we’re only two years apart. The answer, I think, is probably not. I lived about three-quarters of a mile uptown from where she did, and that’s a sizable distance in the urban jungle — though a good friend of mine, who’s three years Kagan’s junior, went to the same (public) high school she did.

But I don’t mean to trip down memory lane here and drag you along with me. What I have been tripping on is the notion, advanced by Sen. Jon Kyl (R-Ariz.), among others, that Kagan’s upbringing — and by extension, mine — puts her out of the American mainstream.

OK, I’ll grant you this — the Upper West Side, especially the Upper West Side of my youth, is a lot more liberal than most places in America. Democrats routinely get 70 percent of the vote or more; when I was growing up, my Representatives in Congress were William Fitts Ryan, followed by Bella Abzug, and then Ted Weiss (Rep. Jerrold Nadler replaced Weiss in Congress, though thanks to redistricting, Rep. Charlie Rangel is now my mom’s Congressman).

All were very liberal. But Ryan was a World War II veteran. Rangel is a Korean War veteran. Weiss’ family fled the Nazis.

Is that out of the mainstream? Whose mainstream? What’s mainstream?

My neighborhood had plenty of wealthy people in it — today it has even more. But it also had Puerto Rican welfare mothers, and young, working-class families, and striving immigrants, and starving artists, and drug addicts and prostitutes on many street corners. In fact, “The Almanac of American Politics” when Kagan and I were teenagers called the Upper West Side “a polyglot area so diverse that it defies accurate description.”

There was an element of danger and decay back then, when Gerald Ford, in a move Jon Kyl might approve of today, told the city, as the Daily News famously reported, to “drop dead.” Whole avenues where prosperous and boisterous young people now roam were off limits to us kids at night because they were too dangerous at the time.

Hardly a Norman Rockwell portrait of America, or a place Jon Kyl might have recognized when he was growing up in Iowa — but a portrait of America nevertheless. Real people, with real struggles — trying to make ends meet, worrying about crime and the schools and making their communities better. Just like any community in America that politicians of all stripes like to rhapsodize about.

Out of the mainstream? Whose mainstream?

Identifying an opponent as “The Other” is one of the oldest tactics in the American political playbook — a tactic that was perfected during the McCarthy era, where you either loved America by denouncing communism or you didn’t. But it seems to be making a comeback in the Republican Party in the era of Obama.

Republicans have legitimate political and policy beefs with Obama, and they’re entitled to them. But there are elements within the GOP that have always sought to discredit him based on his prior relationships with the Rev. Jeremiah Wright and former Weather Underground leader William Ayers, or on the absurd charges that he isn’t a citizen — or that he is a Muslim. Paint Obama as “The Other” and you can erode public confidence in him. And, by the way, did you know that he’s black?

Anti-immigration forces make gains by whipping up fears against “The Other.” While the government reaction to 9/11 was necessarily about national security, it had a more subtle element to it of fighting “The Other.” How many times have Republicans thrown mud at Speaker Nancy Pelosi by reminding audiences that she’s a “San Francisco-style Democrat”? We all know who lives in San Francisco, right? Oh wait, gays and lesbians live in every community in America. Mainstream America.

America, thankfully, is becoming a more diverse and tolerant nation. But we’ve still got a long way to go.

There aren’t too many places left that Norman Rockwell would recognize. Even small towns with white picket fences are populated by Asian and Latino immigrants these days, looking for a better life. But it’ll be a long time before they make their political presence felt.

Every couple of years, Democratic demographers like Ruy Teixeira put out studies that conclude that Democrats will be the ruling party for years to come, pointing to the trends that show minority populations growing and the white population staying the same. They say the presence of Starbucks in rural and exurban communities suggests that more liberal voters are moving there (maybe people in those communities just want strong coffee, too).

But if a permanent Democratic majority is emerging, it’s hard to see it. Republicans still control the megaphone. You’d never hear a Democratic Senator call a Republican nominee for high office out of the mainstream just because he or she grew up in rural Alabama, the way Senate Republicans have with Kagan and her Upper West Side upbringing. That’s example No. 3,047 of Republicans playing political hardball a lot better than Democrats.

In his 1977 masterpiece “Annie Hall,” Woody Allen said that the rest of America looks down on New York City because it thinks the city is populated with “left-wing, communist, Jewish, homosexual pornographers.”

I have no idea whether Elena Kagan will be a good Supreme Court justice. But when she’s confirmed this week I’ll smile on behalf of all my fellow left-wing, communist, Jewish, homosexual pornographers. Score one for our side.