The politics of fighting terrorism are heavily and incontrovertibly stacked against loosening surveillance systems, which is precisely why President Obama, in his speech from the Justice Department on Friday, is likely to insist that Congress share the blame.

The New York Times' Peter Baker is not the first to note how Obama's pre-2008 rhetoric is at odds with his current positions on the NSA's surveillance tools, but his report Thursday morning makes clear that the NSA leaks offered new information to the president as well. "[A]ides said Mr. Obama was surprised to learn after leaks by Edward J. Snowden … just how far the surveillance had gone," Baker writes, including that the cell phones of European leaders were being tapped by the agency. But Baker also points to two moments — reports of a potential attack at Obama's first inauguration and the attempted Christmas Day underwear bombing in 2009 — that, as long-time aide David Plouffe said, put "steel" in Obama's spine.

For the president, there is a massive imbalance between the risk and reward of rolling back the NSA's toolset. If the change to the NSA is the one that the advisory panel Obama convened recommends, the reward is Americans will know that a years-long program of aggregating information about their phone calls has been outsourced to phone companies. And the risk is that the dismantling allows a terror plot to slip through the cracks, and would make President Obama the man who allowed dozens or thousands of Americans to die on his watch — the first president in the post-war-on-terror era to do so.

That's the distinction that Baker draws in his story. Shortly after the failed Christmas attack, Baker writes, "an agitated Mr. Obama 'was extremely firm' with intelligence officials, saying that he 'expected us to do better,' recalled one who was in the room." Had that plane bound for Detroit exploded, Obama at that point could reasonably have pointed to the failures of a system that his predecessor put in place. If one exploded tomorrow, it's unavoidably his fault. If one explodes after he approves a scaleback of surveillance, that defines his presidency.

To some extent, this is why we have a separation of powers, to remove the onus of that decision-making from the president. As The Wire noted on Wednesday, Obama will likely call for Congress to consider reforms to the NSA in lieu of the president acting unilaterally. There's clear evidence that Congress is eager to do so; the government spending bill that passed the House on Wednesday included a measure that blocked funding for a small subset of the NSA's activities. But Congress, unlike the president, wants to be reelected, meaning that they also don't want to set themselves up for months of blistering attacks from opponents about being one of the elected officials who voted to make terror attacks easier.

For Obama and Congress, the reward is very small. A new poll reported by The Guardian suggests that 59 percent of Americans support reforms to the NSA, with 26 percent backing the status quo. Most Americans are skeptical that the NSA won't abuse the information it has. But they could equally be skeptical about the utility of the phone metadata collection: there's been no evidence that it's played any blocking role in block terror activity, and, as The New Yorker reported recently, even claims that it could have prevented 9/11 are overblown.

Interestingly, Obama's speech will preempt a study due out later this month from the Privacy and Civil Liberties Oversight Board, the group established in the wake of the 9/11 attacks to ensure that the government is protecting Americans privacy. The group likely conveyed some of their findings to Obama in a meeting with him earlier this month, but that he's making his recommendation before hearing formally from the privacy advocates is telling.

All of this is predicated on leaked reports suggesting what Obama will say tomorrow. We've been surprised before; the night before his big June speech on climate change, advisors denied he'd talk about the Keystone pipeline, which he did. But the stakes are very different for Obama's presidency between action on the climate and action on terrorism, however unfair that may be. No president will ever want to be the one that made Americans less safe. So, barring an act of enormous strength or a strategy to force others to share the credit or blame, no president is likely to ever turn the ratchet of surveillance very much to the left.