Just a few years ago, climate was all but absent from the national agenda. President Bush's obfuscation efforts are well known, but few national Democratic leaders made much noise about the issue either. Only in 2006, with the ascension of Democrats to majorities in both houses of Congress, did some middling proposals start to bubble up.

Then, in March, John Edwards released a climate and energy plan that came like a bolt from the blue. It targeted greenhouse-gas reductions in the US of 80% by 2050. That would be the rallying cry of activists like those at the nationwide Step It Up protests - a month later. Edwards had taken a stand that was out ahead of the public, the media and even progressive advocates.

Jon Cohn and Ezra Klein tell the same story about healthcare. (See also Klein's great profile of Edwards from Feb.) Matt Yglesias makes the point in general terms:

It's widely noted that there's no enormous policy gap between Hillary Clinton and Barack Obama. Less widely noted is that it didn't always have to be that way. Both Clinton and Obama are running on domestic platforms that are much, much, much more ambitious than anything Al Gore or John Kerry put on the table. And not because Kerry was a notably right-wing Democrat or Clinton a from-the-left insurgent. Rather, the centre of gravity within the party shifted several notches left between the last cycle and this one. In part, that was a response to shifting dynamics in the real world. But to a surprising extent, it was simply a response to John Edwards.

Dana Goldstein ponders where Edwards voters will go (the answer is not as simple as you might think). Ed Kilgore ponders why Edwards lost. And don't miss Christy Hardin Smith's touching farewell.

Here are Clinton's comments on Edwards' exit:

John Edwards ended his campaign today in the same way he started it - by standing with the people who are too often left behind and nearly always left out of our national debate.

John ran with compassion and conviction and lifted this campaign with his deep concern for the daily lives of the American people. That is what this election is about - it's about our people. And John is one of the greatest champions the American people could ask for.

I wish John and Elizabeth all the best. They have my great personal respect and gratitude. And I know they will continue to fight passionately for the country and the people they love so deeply.

Here are Obama's:

John Edwards has spent a lifetime fighting to give voice to the voiceless and hope to the struggling, even when it wasn't popular to do or covered in the news.  At a time when our politics is too focused on who's up and who's down, he made a nation focus again on who matters -- the New Orleans child without a home, the West Virginia miner without a job, the families who live in that other America that is not seen or heard or talked about by our leaders in Washington.  John and Elizabeth Edwards have always believed deeply that we can change this – that two Americas can become one, and that our country can rally around this common purpose.  So while his campaign may end today, the cause of their lives endures for all of us who still believe that we can achieve that dream of one America.

Finally, on a personal note, best wishes to the beautiful, confident, whip-smart Elizabeth Edwards, who out of all the players involved in this extraordinary drama was the one I found most appealing and inspiring.