PITTSBURGH — I'm about to take a propeller plane from here to Harrisburg before heading back to D.C. to cover the election from there.

On the way to the airport, there were few signs that today is a make-or-break election for Democrats Barack Obama and Hillary Rodham Clinton, though local radio was talking up the primary and featured interviews with the candidates and their surrogates.

The forecast is clear and it is indeed beautiful as voters head to the polls, which opened at 7 and will close at 8 p.m.

Even Obama supporters are fairly certain Clinton will win tonight, and the race will continue into May. But the high number of undecideds - still! - could swing the result in a different direction. We'll know soon enough.

I've had the impression for a while that folks attending Obama rallies are true believers, but that theory was proven wrong this morning.

When you buy one-way tickets at the last minute, you tend to get flagged for extra screening, and today was no exception for me. So I made the most of it and interviewed my TSA screener.

Here's how the conversation went, similar to so many I've had in recent days.

Me: So, are you voting today?

Screener: You bet.

Me: Which candidate do you like?

Screener: I just don't know. Probably Hillary.

Me: Interesting. What do you like about her?

Screener: I'm just not sure, there are things I like about both of them. I got to see Obama at an event. He got me all enthusiastic that day.

Apparently not enthusiastic enough to close the deal.

I have a story in today's paper exploring what Clinton needs to do today in order to remain in the nomination battle.

McKEESPORT, Pa. - Sen. Hillary Rodham Clinton dominated Ohio, squeaked out a win in the Texas primary and is looking for a solid victory today in Pennsylvania to keep superdelegates from breaking for her Democratic presidential rival and finally ending the nomination battle.

If she gets the big win, she'll have more evidence for her claim that Sen. Barack Obama is unable to deliver in major swing states and, her team says, it will raise serious questions about his electability.

"It's safe to say that, certainly, the superdelegates will have several questions for the Obama campaign if Senator Obama fails to be successful on Tuesday, considering the amount of resources they've expended on Pennsylvania," said Clinton spokesman Phil Singer.

But the size of Mrs. Clinton's expected victory here today is more important than the win, and the tipping point for her viability for staying in the race ranges from a five-point to double-digit victory, depending on the source.

"If she gets a 20-point win, that would be impressive," quipped Obama strategist David Axelrod, citing her one-time massive lead when the Pennsylvania campaign began.

Read the rest here, and a story on the candidates' closing arguments, here.

— Christina Bellantoni, national political reporter, The Washington Times