As the 10th anniversary of the Guantanamo Bay military prison on Cuba was marked this week, some commentators noted that candidate Barack Obama had promised to close the facility, but has failed to do so as president. Another Obama promise deserves attention — the promise to scrutinize the federal budget, going through it “line by line” to find — and root out — unnecessary spending.

At this time of intense budget pressures, American taxpayers would like to believe that every dollar the federal government spends is well spent. They don’t.

In 2008, Obama said that his Office of Management and Budget “will go through our federal budget — page by page, line by line — eliminating those programs we don’t need, and insisting that those we do operate in a sensible cost-effective way.”

The “line-by-line” pledge inspired hope that wasteful, duplicative or politically motivated spending would be stripped from the federal budget. It hasn’t happened.

The president’s 2009 budget included a section titled “Terminations, Reductions and Savings,” which amounted to $17 billion. Normally, $17 billion sounds like a lot of money. But in the context of a $3.6 trillion budget, that $17 billion is less than half a percent of spending.

As the country continues to endure the aftermath of a financial crisis and painful recession, government spending has come under greater scrutiny. Most taxpayers have had to tighten their belts at home and at work, and most would expect that the president’s fiscal watchdogs could come up with more than a 0.47 percent budget savings.

Who can believe that the “line-by-line” critical analysis promised by Obama has happened? It’s possible that the budget sleuths found some bigger savings, but the president’s political advisers recommended killing those cost-saving ideas because they would anger some constituencies important to the president’s re-election effort.

Many business owners and managers who have made difficult spending reductions in the past few years must have trouble believing that 99.53 percent of the federal budget is considered essential expenditures. Many business operators have had to actually reduce spending, whereas many conversations about the federal budget talk about spending reductions when the reality is only a slowing of the rate of spending growth.

The problem is that for every dollar of federal spending there is a constituency that views it as essential. That constituency could be the agency employees themselves or officials benefiting from federal funding for some local project, no matter how questionable in the eyes of people outside the area. Other difficult places to cut spending could be the tax breaks that lobbyists have had inserted into the federal tax code with the help of members of Congress whose re-election campaigns they fund with corporate and special-interest donations.

Cutting spending from the federal government’s bureaucracy is a huge challenge because of the sheer size and scope of it. Obama promised to do it, but failed to make a significant dent. And former President George W. Bush, presumably a fiscal conservative, allowed federal spending to grow dramatically during his administration.

It’s easy — and politically popular — to say yes to more spending. It’s hard — and often politically unpopular — to reduce spending. That’s why politicians, at every level, rarely do it.

But American taxpayers are desperate for a serious going- over of the federal budget, just like the one Obama promised.

Taxpayers are still waiting for that tough “line-by-line” examination.