From the AP: Barack Obama has effectively clinched the Democratic presidential nomination, based on an Associated Press tally of convention delegates.

The tally put Obama over the top Tuesday, ahead of the results from the day's final primaries in Montana and South Dakota. The Illinois senator becomes the first black candidate ever to lead his party into a fall campaign for the White House.

Obama outlasted former first lady Hillary Rodham Clinton in a historic contest and now faces Republican Sen. John McCain of Arizona for the presidency.