The impact of a single endorsement in a political campaign is debatable.
Does the opinion of one person, whether it's a big name political leader like Jimmy Carter or Al Gore or a bleached blond D-List reality TV star like Heidi Montag, actually matter to voters? Will an endorsement help a voter make up their mind? Change their mind? Get them to the polling station?
Basically, endorsements matter unless they don't. But the free media that an endorsement provides may be more valuable and have more legs than the announcement itself.
Take Bill Richardson's bombshell that he was backing Barack Obama. This was seen as a coup for Obama because of Richardson's ties to the Clintons and marked the second former Democratic rival to get in his corner (after Chris Dodd). Though it came over two weeks too late to be helpful in Texas, Richardson's support could be key to bringing Hispanic voters onto the Obama campaign.
Richardson's endorsement was two weeks ago – an eternity in politics. Yet his name (and support for Obama) is still in the headlines and the endorsement continues to reverberate through the campaign because Team Clinton, clearly still smarting, keeps putting it back in the news. From James Carville's Judas comments, to Bill Clinton's reported red-faced rant, to Hillary Clinton declaration that Obama "cannot win" the general election, the media gets to regurgitate the "Richardson is on Team Obama" storyline.
Today Hillary Clinton denied that she told Richardson that Obama "cannot win" a general election against John McCain.
"That's a no," Clinton told reporters at the end of a press conference in Burbank, CA, when asked if made the comment to Richardson, per ABC News' Eloise Harper.
"We have been going back and forth in this campaign of who said what to whom and let me say this, that I don't talk about private conversations but I have consistently made the case that I can win," she said.
ABC News' George Stephanopoulos reported on Wednesday's World News that sources with direct knowledge of the conversation between Sen. Clinton and Richardson, prior to the Governor's endorsement of Obama say she told him flatly, "He cannot win, Bill. He cannot win."
Martin Luther King Jr. Anniversary
Friday is the 40th anniversary of the assassination of Dr. Martin Luther King Jr. and both Hillary Clinton and John McCain will detour from the campaign trail to make appearances in Memphis.
Clinton posted a video tribute to Dr. King on her campaign's web site, recalling how she heard him speak in Chicago when she was a young girl. "He called his sermon that evening 'Remaining Awake Through a Great Revolution.' Dr. King challenged all of us there, as he did throughout his life, to stay awake during the great civil rights revolution that was sweeping our country."
McCain will deliver remarks to the Southern Christian Leadership Conference and lay a remembrance wreath National Civil Rights Museum at the former Lorraine Motel where King was assassinated.
ABC News' Jake Tapper writes about McCain's "complicated history" with Martin Luther King Jr. Day – as a young congressman in 1983, McCain voted against legislation designating a federal holiday for the civil rights activist.