Why the Kennedy Endorsement Matters

This election holds special meaning for so many:

Rejecting a personal entreaty from President Bill Clinton, Sen. Edward M. Kennedy (D-Mass.) plans to endorse Sen. Barack Obama (D-Ill.) for president in a joint appearance on Monday, Democratic sources said.

Democrats said the endorsement will help Obama with traditional Democratic groups where Clinton has been strong -- union households, Hispanics and downscale workers.

Also, the nod by the most experienced member of the Senate adds significant standing to Obama, who is working to prove he has the experience necessary to be president.

The announcement stunned Senate colleagues, who had expected Kennedy to remain neutral until the increasingly vitriolic nominating contest with Sen. Hillary Clinton (D-N.Y.) settled out.

"This is the biggest Democratic endorsement Obama could possibly get short of Bill Clinton," said a high-level Democrat.

The Clinton campaign launched a last-ditch effort over the last few days to stop Kennedy's move, orchestrating a flood of phone calls to Kennedy from sources ranging from union chiefs to his Massachusetts constituents.

The former president also called Kennedy in a vain attempt to keep him out of the race, a source familiar with the conversation said.

During his two terms in the White House, President Clinton made repeated overtures to the Kennedy family. So the senator's rejection of his wife is at least as embarrassing as her 28-point loss in the South Carolina primary on Saturday.