by Doyle McManus

In politics, a week is a lifetime.

One week ago, Barack Obama was on the verge of wrapping up the Democratic nomination by winning Texas and coming close in Ohio. Except he didn’t. The arithmetic still gives Obama a better chance at winning the nomination than Hillary Clinton, but it’s no longer a lock. If Clinton can persuade her party to admit delegates from Michigan and Florida, where she won primaries held in violation of party rules, she could inch ahead in the elected delegate count. (And she just might win that argument. Last month, the Los Angeles Times/Bloomberg Poll found that most Democrats think the Michigan and Florida delegates should be allowed in.) If Clinton edges into the lead based on those contested delegates in an angry controversy, what would the superdelegates do then?

That’s only one week’s worth of twists and turns. Think about how different the landscape looked only a few months ago.

A Los Angeles Times/Bloomberg Poll in October gave this picture: Among Democrats, Clinton was ahead of Obama by a huge 31 point margin, 48% to 17%, and was “solidifying her lead” (to quote our analysis at the time). Clinton was ahead of Obama among black voters as well as white voters.

On the Republican side, former New York Mayor Rudy Giuliani was the clear front-runner, with 32% to McCain’s 13%. The McCain campaign, given up for dead last summer, was showing signs of life – but the stories we produced at the time described that more as an odd curiosity (“He’s still alive!”) than as the first stirrings of a juggernaut.

What lessons can we draw from this remarkable year? Here are 10: