Then-Democratic presidential hopeful Sen. Barack Obama  smiles with Sen. Ted Kennedy (D-Mass.) during a rally at American University in Washington on Jan. 28, 2008. (Charles Rex Arbogast/AP)

Seven years ago, Ted Kennedy changed the course of the 2008 Democratic presidential primary. He endorsed Barack Obama over Hillary Clinton.

Here's the key passage from Kennedy's speech that late January day at American University:

There was another time, when another young candidate was running for president and challenging America to cross a New Frontier. He faced public criticism from the preceding Democratic president, who was widely respected in the party. Harry Truman said we needed "someone with greater experience" — and added: "May I urge you to be patient." And John Kennedy replied: "The world is changing. The old ways will not do ... It is time for a new generation of leadership."

So it is with Barack Obama. He has lit a spark of hope amid the fierce urgency of now. I believe that a wave of change is moving across America. If we do not turn aside, if we dare to set our course for the shores of hope, we together will go beyond the divisions of the past and find our place to build the America of the future.

Obama had been hinting at the Kennedy connection, rhetorically, for months. But to have the brother of John and Bobby Kennedy tell the Democratic party — and the country — that the junior Illinois senator was the heir to he and his brothers' political legacy was a momentously powerful moment. (The Kennedy endorsement of Obama is a "symbolic" endorsement, the top of the Fix's endorsement hierarchy.)

The endorsement came at a critical time for Obama; he had won the South Carolina primary by almost 30 points over Clinton two days earlier. It had begun to dawn on everyone that he just might be the nominee. Kennedy's endorsement codified that sense, fueling momentum and energy that helped Obama virtually sweep the caucuses that populated the calendar that February and, in so d0ing, build an unassailable delegate lead.

Of course, it's entirely possible that Obama could have — and would have — won without Kennedy's help. After all, Obama won the Iowa caucuses going away in early January — and then the South Carolina primary — without any help from Kennedy or his clan. (Kennedy died in August 2009.) But the symbolic import of the torch-passing from Kennedy to Obama is hard to overestimate in the context of a race in which one of the young Illinois senator's main hurdles was convincing people that the Clintons, the reigning first family of Democratic politics, could possibly be beaten.  The Kennedy blessing mattered. Hugely.

That moment is surely on Obama's mind as he delivers the keynote speech at the opening of the Edward M. Kennedy Institute today in Boston.

Watch Kennedy's full speech endorsing Obama. It's a remarkable piece of political history.