Washington — The race for the White House began almost 2 1/2 years ago — some would say even earlier.

Now, what is already the longest, costliest presidential campaign in U.S. history is only three months away from its conclusion.

In those final months leading up to the Nov. 4 election will come events that, as much as anything that preceded them, could determine the outcome of the contest between Democrat Barack Obama and Republican John McCain.

The political landscape is widely believed to favor Obama. Still, neither candidate has made the sale. Polls show the twowithin a few percentage points of one another, with McCain — who has made comebacks before — potentially poised for yet another.

It will likely all come down to the sprint for the finish.

Here are some potentially decisive moments to watch for.

FRIDAY

The Olympics begin in Beijing, during which the Obama campaign plans to air $5 million in TV ads. The McCain campaign has declined to disclose whether it will follow suit.

BETWEEN NOW AND AUG. 25

Obama is expected to name his running mate before the Demcratic National Convention begins. Precisely when remains in doubt. Newsweek reports that his recent overseas trip set back the vetting process and that he may not make an announcement until the week of Aug. 17.

AUG. 25

The Democratic National Convention convenes in Denver, culminating in Obama's acceptance speech on Aug. 28 at Invesco Field at Mile High Stadium.

AUG. 29

McCain turns 72, a birthday that highlights the fact that, if elected, he will be the oldest first-term president in American history. With the Democratic convention over and his about to begin, this might be the perfect time to divert attention by naming a running mate.

SEPT. 1

The Republican National Convention begins at Xcel Energy Center in St. Paul, with McCain set to accept the party's nomination on Sept. 4.

SEPT. 11

The seventh anniversary of the 9/11 terrorist attacks, which both candidates are likely to use to reiterate their positions on the war in Iraq — that Obama opposed it from the start, that McCain supported the surge that has been credited with reducing the violence in the war.

SEPT. 15

The deadline by which the last of the "surge" troops in Iraq will have been withdrawn, triggering a 45-day "pause" for U.S. commander Gen. David Petraeus to determine if it is possible to further reduce the 140,000 U.S. force in Iraq.

SEPT. 18

Google/YouTube hosts a town hall meeting for the presidential candidates in New Orleans, with the city's post-Hurricane Katrina problems likely to be part of the discussion.

SEPT. 26

The Commission on Presidential Debates hosts the first of three presidential debates, on domestic issues, at the University of Mississippi in Oxford.

OCT. 2

The vice presidential candidates debate at Washington University in St. Louis.

OCT. 7

The commission hosts its second debate, a town hall format, at Belmont University in Nashville.

OCT. 15

The commission hosts its final debate, on foreign policy, at Hofstra University in Hempstead, N.Y.

OCT. 30

The Commerce Department issues its advance estimate of the third-quarter of the Gross Domestic Product, an indication of the economy's health.

NOV. 4

Election Day.

RECENT NATIONAL POLLS

Barack Obama 47%

John McCain 41%

Und./other 12%

— AP/Ipsos poll of registered voters

Barack Obama 47%

John McCain 43%

Und./other 10%

— Gallup poll of registered voters

John McCain 47%

Barack Obama 46%

Und./other 7%

— Rasmussen poll of likely voters

Barack Obama 51%

John McCain 44%

Und./other 5%

— CNN poll of registered voters

John McCain 49%

Barack Obama 45%

Und./other 6%

— USA Today/Gallup poll of likely voters