IT'S ONLY, unoffically, a few hours old, but one thing is already clear about the general election for president in 2008: American voters can't complain about not having a real choice.

The fall campaign will pit the oldest first-time nominee for the White House against one of the youngest, who is seeking to become America's first black president.

One candidate supports the U.S. mission in Iraq, the extension of President Bush's tax cuts, and opposes abortion. The other supports abortion rights, would raise levies on the richest Americans, and has vowed to bring the troops home from the Gulf conflict as soon as he can.

Their stories are both American pie, but very different tasting slices: The admiral's-son-turned-prisoner-of-war Vietnam hero versus the immigrant's son who went from food stamps to the Ivy League.

Democratic U.S. Sen. Barack Obama of Illinois against Republican U.S. Sen. John McCain of Arizona already shapes up as one of the most epic battles for the presidency in U.S. history - to steal a phrase from Delaware's Sen. Joe Biden: "It's storybook, man."

The world woke up to history today as Obama - gaining a steady stream of key superdelegate endorsements throughout the day - finally claimed victory in his long and often bitter fight for the Democratic nomination against a determined U.S. Sen. Hillary Clinton, the former First Lady.

The 46-year-old Obama told a screaming throng in St. Paul, Minn., in the very hockey arena where the GOP will nominate McCain in September, that "tonight we mark the end of one historic journey with the beginning of another - a journey that will bring a new and better day to America.

"Tonight, I can stand before you and say that I will be the Democratic nominee for President of the United States," said Obama, who was born in 1961, when many blacks were still prevented from voting across the American South.

A stream of new support from the key party insiders who serve as superdelegates to the Democratic convention in Denver in August - from Philadelphia party boss Rep. Bob Brady to ex-president Jimmy Carter - finally clinched the nomination for Obama, even as he suffered an embarassing primary loss to Clinton in South Dakota.

McCain immediately took up the general election fight in a speech to his supporters 1,000 miles downriver in New Orleans, where he acknowledged Obama's victory and battled back against Democratic attempts to tie him to Bush.

"They've seen me put our country before any President - before any party - before any special interest - before my own interest," McCain said. "They might think me an imperfect servant of our country, which I surely am. But I am her servant first, last and always."

McCain also made a surprising appeal to Clinton supporters, aware that some will be disgruntled and are considering voting for the GOP standard bearer in the fall.

"The media often overlooked how compassionately she spoke to the concerns and dreams of millions of Americans, and she deserves a lot more appreciation than she sometimes received," McCain said last night.

Clinton's future course of action was a little more unclear last night.

"This has been a long campaign, and I will be making no decisions tonight," Clinton told her supporters last night in a speech in Manhattan, continuing to give out her Web site address.

But already speculation was moving rapidly to the vice presidential selection process - fueled in part by Clinton's reported remark to New York's congressional delegation that she'd be open to the No. 2 slot.

Political experts said such a move could reunite the fractured party - but also raised new questions about the role of ex-President Bill Clinton in a such an arrangement.

Many experts expect Obama to seek someone who'll counter his perceived inexperience in military and foreign affairs - someone like Virginia's U.S. Sen. Jim Webb, the former Secretary of the Navy, or retired Gen. Ramsey Clark.

For McCain, 71, according to most pundits, the challenge is different - bringing in some combination of youth or a change agent or both. That could mean turning to Louisiana's new, young Indian-American Gov. Bobby Jindal or even ex-Hewlett Packard CEO Carly Fiorina.

Once that key piece of summer business is settled, the candidates will turn their attention to a November election map that looks somewhat different from the familar red-and-blue patterns of the last couple of presidential races.

That means McCain will try to exploit Obama's unpopularity in Appalachia while the Democrat will appeal to increasingly independent-minded voters in the Mountain West and in border states like Virginia.

One thing seems obvious - Pennsylvania, with its 23 electoral votes, will be a critical battleground state, visited frequently by both major candidates.

"It looks like Pennsylvania is going to be a major decider of the presidential election," said G. Terry Madonna, the political scientist and pollster from Franklin and Marshall College.

That's despite the fact that Democrats Al Gore and John Kerry won the Keystone State in the last two elections, and the GOP appears more hampered by the weak economy.

Madonna said he expects McCain will make a major play for two key voting blocs where Clinton beat Obama in the April Democratic primary. One is western Pennsylvania, bastion of blue-collar voters known as "Reagan Democrats," and the other is the Philadelphia suburbs, home of white-collar "Rendell Republicans" where McCain is viewed as more moderate on social issues than Bush has been.

One wild card for Obama - both in Pennsylvania and in other key states - is whether the first major African-American nominee will continue to be the target of viral e-mail campaigns that have appealed to racism or to false allegations that Obama is a Muslim.

"If Obama loses there will only be two reasons, given the favorable conditions for Democrats," said Larry Sabato, the University of Virginia historian and presidential pundit. "One is his relative inexperience, which is legitimate, and the other is race, which is not legitimate. The combination of those two could be toxic."

But Kareem Clayton, professor of law and politics at the University of Southern California, said that McCain also goes into the fall campaign with some liabilities - not just his ties to the Bush policies in Iraq and on other issues but also the sense from the Christian right that he's too liberal.

"Social conservatives are not entirely sure that he's one of them," said Clayton. But he also predicted that McCain could rectify that problem by emphasizing the Supreme Court and GOP fears that a Democratic president may pick several new justices. Most polls have shown that five months from the general election, the race between McCain and Obama is neck and neck, with the Electoral College map perhaps slightly favorable to the Republican. *