There is no doubt that if Democrats lose the Kennedy seat in Massachusetts in the special election on Tuesday, that Barack Obama's road to re-election suddenly looks like Hamburger Hill. He will be fighting for his political life for the rest of his term.
Ted Kennedy's death seemed little cause for concern at the time, and a Democratic successor seemed a certainty. Now, it may be the hinge of history that unhinges a second Obama term.
The importance of what is at stake is evident from the fact that Bill Clinton and Obama have now found it necessary to go to Massachusetts to campaign for Martha Coakley, which shows this race is tighter than a tic.
If Martha Coakley loses, then health care is almost certainly dead in the water, as well as a raft of changes Obama was anxious to bring about. Much of his domestic agenda, including issues like immigration reform, will be in ruins.
The word will go forth that Democrats are an endangered species, that the electorate is sick and tired of big spending, and that it is not a time for big government, but small incremental changes.
That will all come about if Coakley loses. The irony is Kennedy's seat must have been considered the safest of all on the Democratic checklist.
His death and Coakley's insipid campaign has opened up a nightmare scenario for Obama, in which a second term becomes a massive struggle
Kennedy giveth, and now he may be about to take it away.