THAT "YOUTH VOTE" you hear so much about?

I wonder if it's here and if it makes a difference.

Seems pretty clear that Campaign '08 overall has been marked by a surge of younger voters.

But here? And impacting the state's April 22 primary?

Well, if so, older voters handing an edge to Hillary Clinton could get counterbalanced by youth for Barack Obama.

New state registration figures show 398,088 Democrats aged 18 to 24 and another 653,882 Democrats aged 25 to 34.

I suspect these are record highs.

The new Democratic registration of 4,189,955 is a record, but the state says it never kept tabs by age before.

The 18-to-34 vote now makes up 26 percent of the Democratic vote; the 65 and older vote is 21 percent.

Also, lots of college kids: 680,000, according to the state Department of Education, the large majority of them Pennsylvania residents, at 251 colleges and universities - more than any state but California and New York.

We don't know if they'll vote (though this year's trends suggest they will) or, if they do, for whom (though this year's trends suggest Obama).

The problem is that pollsters have a tough time measuring, even finding, the youth vote.

Realities of life: Older people tend to be home and answer the phone; younger people tend not to have landlines, and no one does cell-phone polling.

So, who knows what's really out there?

This week's Quinnipiac Poll, for example, shows Clinton up 6 percentage points statewide but Obama leading among the 18-44 age group by 15 points.

That wide age spread suggests to me that Quinnipiac couldn't get a good sample among voters 18 to 24 or even 18 to 34.

But Quinnipiac's Clay Richards tells me that younger voters are accurately represented by weighting their numbers against census data, and that the 18-44 age spread had been used because "that seems to be the [age] break between Obama and Clinton [supporters]."

He adds that the lower the age, the stronger Obama's support.

Registration figures say that 18 to 44 year olds make up 43 percent of the state's Democratic electorate.

Is there a wellspring of support for Obama that doesn't show up in polls?

Richards concedes that young voters are hard to poll: "Yeah, they're not around."

Others go further.

"Young voters are typically under-represented in most polls," says pollster Neil Newhouse, of Public Opinion Strategies.

"That's especially true in these primaries," he says, "because younger voters have not traditionally voted in heavy numbers in primaries, so there's little historical data to indicate what percentage of the primary vote they should be."

That could be changing.

Newhouse says that, overall, Democratic primary turnout is up 110 percent this year over 2004, but that the 18-to-29-year-old vote is up 192 percent.

And when younger voters are asked to grade their level of interest in the '08 race on a scale of one to 10, more than half of 18 to 34 year olds (51 percent) say it's "10." In '04, that number was 39 percent. And more than half of 30 to 34 year olds (57 percent) say it's "10." In '04, that number was 46 percent.

Older age groups show much lower levels of increased interest.

"Younger voters are a significantly bigger chunk of the electorate than in the past," Newhouse tells me.

As always, it comes down to turnout. Historically, younger people vote least, older people vote most.

So the question is whether this year is different.

I've seen and heard lots of anecdotal evidence that the race is dividing as much on generational lines as on gender or race.

Given state numbers, there's at least potential for a youth vote impact.

And it seems that that vote, either way, could determine the outcome. *

Send e-mail to baerj@phillynews.com.

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