W ASHINGTON (Reuters) – In the waning days of his presidency, George W. Bush listed the failure of immigration reform as one of his biggest disappointments and deplored the tone of the immigration debate. It had, he said in December 2008, undermined "the true greatness of America which is that we welcome people who want to work".

The way things look a year and a half into the administration of Barack Obama, he too may end his presidency deploring the failure to fix America's dysfunctional immigration system. The tone of the debate is even more rancorous now than it was when Bush pushed reform and it features the same arguments, including the fantasy that you can fully control the frontier between the US and Mexico, the world's busiest border.

That illusory target was set in the Secure Fence Act of 2006, signed into law by George W. Bush on October 26 of that year. It provided a definition of the term "operational control", one of the most frequently used buzz phrases of the debate. (The other is "securing the border"). Under the letter of the law, operational control means "the prevention of all unlawful US entries, including entries by terrorists, other unlawful aliens, instruments of terrorism, narcotics, and other contraband."

Note the word "all". Then contrast it with what is at stake: almost 7,500 miles of land borders (with Mexico and Canada), 12,300 miles of coastline and a vast network of airports, seaports and land crossings. In the long-running debate, sound bites alone could fill a library and one of the best came from Janet Napolitano when she was governor of Arizona: "Show me a 50-foot wall and I show you a 51-foot ladder."

That quote has history on its side. There has never been an impenetrable border. Not the Great Wall of China, the 5,500-mile mother of all walls, not the Berlin Wall, not the Iron Curtain, the lethal system of walls, fences, minefields and watch towers manned by guards with shoot-to-kill orders that sliced 2,500 miles through Europe.

Napolitano, now head of the Department of Homeland Security, the 160,000-strong bureaucratic behemoth charged with ensuring "operational control", no longer uses the wall-and-ladder simile. Instead, she talks of the need for "comprehensive immigration reform", as does her boss, Barack Obama, and as did George W. Bush.

Bush's attempt to push through a reform addressing all aspects of the complex, emotion-laden issue fell through because he could not convince legislators in his own Republican party that there should be a path to citizenship for the estimated 11 million illegal immigrants already in the United States. Obama does not have enough votes in the Senate for a reform bill.

And leading Republicans insist that there must be a sequence in any changes to what everybody agrees is a broken system. "First...we have to secure the border. If you want to enact other reforms, how can that be effective when you have a porous border," says John McCain, the Arizona senator who once championed an all-encompassing package. He and others have not explained what exactly they mean by "secure border". If that stands for keeping "all" illegal crossers out, it's difficult to see how there could ever be reform. Largely symbolic gestures, such as Obama's decision in May to send 1,200 National Guard troops to the border with Mexico, will make little difference on the ground.

By ordering the troops' deployment, Obama trod in the footsteps of Bush, who dispatched 6,000 National Guard troops to the border in 2006 to back up the Border Patrol and help build several hundred miles of walls and fences. In both cases, the measures were meant to win bi-partisan support for overall reform.

That would need to include figuring out a way to keep track of people who enter the U.S. on valid visas and stay behind when they expire. With attention focused on the border, visa overstayers rarely figure in the debate but they are estimated to make up around 40 percent of the population of illegal immigrants. How to handle them has been the thorniest problem of all, with conservatives decrying as "amnesty" proposals to work out a way to legal status. Public attitudes are somewhat schizophrenic, judging from opinion polls. A poll late in May by the Opinion Research Corporation, for example, showed 80 percent in favour of a programme that would allow illegal immigrants who have already lived in the US for several years to apply for legal status if they had a job and paid any taxes owed. But in response to a differently-phrased question, 60 percent supported deporting illegal immigrants already in the country.

Last year, according to government figures, the US deported 387,790 illegal immigrants — an average of more than 1,000 a day and a tiny fraction of the undocumented population. Wholesale deportation of all of it belongs as much in the world of fantasy as the idea that "all unlawful entries" could be stopped.

To show how unrealistic the notion of mass deportation is, the Center for American Progress, a liberal Washington think tank, crunched some numbers in a recent report on immigration. Assuming that they could all be tracked down, how many buses would it take to ferry out all illegal immigrants? Around 200,000. Placed bumper-to-bumper, the buses would stretch 1,800 miles.