The first Gallup tracking poll shows that Mitt Romney, after having emerged from an at-times brutal primary process, holds a slight lead over President Obama, 47 percent v. 45 percent. That must be disconcerting to those on the left, who believe that Obama is nearly a lock for re-election.

He’s clearly not.

To make matters worse for the president, 2012 will — in the words of former Clinton aide William Galston – be a “referendum, not a choice.” But most ominously for Obama is this paragraph:

Obama is no longer the master of his fate. During the 2008 campaign, Obama could and did seize the initiative in the face of unexpected events. His agile response to the mid-September financial meltdown propelled him into a lead that he never surrendered. In 2012, by contrast, he will be at the mercy of events that he cannot control. The Supreme Court will decide the fate of the Affordable Care Act. A military confrontation between Israel and Iran would put the administration in the no-win situation it has struggled to avoid, with incalculable consequences for our national security as well as our politics. If job creation returns to the strong pace of the late winter and remains there through the fall, he will be reelected with room to spare. But if the middling March employment report is a harbinger of things to come, the electorate’s evaluation of his performance will be harsh, and the road to reelection very steep indeed.

No politician wants to be in a position where he’s not the master of his fate. More than most presidents seeking re-election, though, that’s the situation Obama finds himself in. To win re-election, Obama needs most things to go right for him and most things to go wrong for Governor Romney. That scenario isn’t out of the question, but it’s not a terribly comforting thing to have to base your re-election on. Yet it’s all the president has right now. A record of nearly uninterrupted failure will do that to a campaign.