Hillary Clinton defeats Barack Obama in Pennsylvania, and so the Democratic Party’s excitement — and agony — continues.

She won and yet Rep. Patrick Kennedy, who backs Obama, says, “It’s going to be basically impossible for Obama to lose his lead when you look at pledged delegates.”

I agree. This could go on until the last primary in June and Clinton won’t be able to make the math work, her only hope being to convince so-called superdelegates to side with her anyway; that could bring new turmoil.

A prolonged fight damages the party. Rhode Island Democratic chairman William Lynch, a Clinton fan, deserves creativity points for explaining why he still likes the Democrats’ chances against Republican John McCain. Saying the Democrats easily have the two best candidates, Lynch cites baseball’s postseason: “It’s like watching the Red Sox and Yankees go toe to toe for 7 games, 9 innings a game. Somebody wins by one run and then they go play the Colorado Rockies.”

You could argue that Clinton herself is two candidates: Ms. Nice and Ms. Nasty. There’s the elated, uplifting granddaughter of a Scranton lace mill worker and daughter of a Penn State football player, who said Tuesday night, “I only wish they could have lived to see this moment.”

In her victory speech, she also said, “Not long ago, a woman handed me a photograph of her father as a young soldier. He was receiving the Medal of Honor from President Truman at the White House. During World War II, he had risked his life on a daring mission … In the corner of that photo, in shaky handwriting, this American hero had simply written, ‘To Hillary Clinton, keep fighting for us.’ And that’s what I’m going to do…”

On CNN, Clinton ally Paul Begala liked the positive, emotional tone. Usually, he said, “There’s about two feet of bulletproof glass between her heart and that camera.” Worse, in an editorial yesterday, “The Low Road to Victory,” The New York Times, which backs Clinton’s candidacy, said her attack approach in ads and interviews is mostly to blame for the “mean, vacuous, desperate, pander-filled” tone of the nomination contest. The Times said this hurts her, Obama, the party and the election.

Bill Lynch says The Times can carp. “But Hillary Clinton won by 10 points in Pennsylvania.”

Lynch says negative ads work. Still, the more bitter the Democrats get, the more diminished will be the nominee. But there are other reasons Democrats should worry, one of them especially if Obama is the pick. For America, the most troubling thing to emerge in Pennsylvania is the prospect that race may play an ugly role this fall. Sure, blacks voted overwhelmingly for Obama, and you can call that pride, or you can be critical of that too. But what caught my eye was that exit polling showed Clinton besting Obama 60 to 40 among whites. This is actually a small improvement for Obama over Ohio. Still, as reported in a Times story on Pennsylvania, “Sixteen percent of white voters said race mattered in deciding who they voted for, and just 56 percent of those voters said they would support Mr. Obama in a general election; 27 percent of them said they would vote for Mr. McCain if Mr. Obama was the Democratic nominee, and 15 percent said they would not vote at all.”

Even so, Kennedy says the Bush-led GOP is leaving an economy in “shambles” and a country “suffering terribly” from the Iraq war.

On election day, Kennedy says, “I frankly don’t think people will care what color Obama is.”

M. Charles Bakst is The Journal’s political columnist.

mbakst@projo.com