WASHINGTON (CNN) -- In what he called a "defining moment for our nation," Sen. Barack Obama on Tuesday became the first African-American to head the ticket of a major political party. Sen. Barack Obama on Tuesday told supporters he will be the Democratic nominee. Obama's steady stream of superdelegate endorsements, combined with the delegates he received from Tuesday's primaries, put him past the 2,118 threshold, CNN projects. "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," he said. "Tonight, I can stand before you and say that I will be the Democratic nominee for president of the United States." Watch Obama say he'll be the nominee »
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NEW: Clinton says she's not making any decisions tonight
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NEW: CNN projects Clinton wins South Dakota; Obama takes Montana
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Obama passes delegate threshold
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Clinton tells New York lawmakers she would be Obama's No. 2
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