There is a saying that America is always preparing to fight the last war. So it is with the conservative crusade against illegal immigration. After all, even as Tea Party Republicans demand draconian--and expensive-- new "border security" measures, apprehensions of the undocumented have plummeted to 40 year lows. And thanks to the slow U.S. economy recovery, the faster GDP growth south of the border and the aging of the Mexican population, the days of a million plus apprehensions a year are almost certainly over. Nevertheless, Republicans are demanding a doubling of the border security force and 700 miles of new fencing as the price for finally lifting the shadow hanging over 11 million undocumented people in the United States.

While the Congressional Budget Office explained that immigration reform along the lines of the current Senate bill would improve Uncle Sam's finances by hundreds of billions of dollars over the next two decades, the Wall Street Journal admonished its Tea Party cousins for their fixation on the rapidly shrinking problem of illegal border crossings:

The U.S.-Mexico border is more secure today than it has been in decades. According to Border Patrol statistics, illegal entries are at a 40-year low. Apprehensions of illegal entrants exceeded 1.1 million in 2005, but in both 2011 and 2012 the number was below 365,000.
According to a study by the Government Accountability Office, the number of illegal immigrants who escaped capture at the nine major crossing points from San Diego to El Paso fell an astonishing 86% between 2006 and 2011. All the talk-show shouting about America under siege from immigrants streaming across the Rio Grande is fiction.

But leaving aside for the moment the arguments as to why comprehensive immigration reform is the right thing to do, there can be little doubt that this is the right time to do it. After all, over just the past few years the population of undocumented immigrants has dropped from 12 to 11 million. By last year, the U.S. recession, stepped up border security, the growing Mexican economy and aging Mexican population combined may have produced a net outflow of undocumented workers. The result, contrary to conservative mythmaking, is an undocumented population over 60 percent of which has now been in the United States for over a decade.

That illegal immigration into the U.S. has plummeted is indisputable. As the Washington Post reported in December 2011, "The Border Patrol apprehended 327,577 illegal crossers along the U.S.-Mexico border in fiscal year 2011, which ended Sept. 30, numbers not seen since Richard Nixon was president, and a precipitous drop from the peak in 2000, when 1.6 million unauthorized migrants were caught." But as the New York Times explained in January, that shift may continue even after the U.S. economy fully recovers:

By some key measures, the problems underlying illegal immigration --the economic and demographic pressures that have drawn Mexicans north for decades in search of jobs and a better life, and the challenges for the United States of securing its borders -- have diminished over the past six years.
The Mexican economy, while still riddled with inefficiency and inequality, is nonetheless humming along, providing many more job opportunities for Mexican workers. And in Mexico, the source of about 6 in 10 illegal immigrants in the United States, the birthrate has plummeted over the last few decades, shrinking the pool of potential emigrants.

To be sure, the ramped-up security at the border and aggressive immigration enforcement begun President Bush and expanded under President Obama has had a major impact. Deportations have surged under Obama, with the number hitting 409,000 in 2012 alone. As a recent report from the Migration Policy Institute revealed, "during the 2012 fiscal year, the federal government spent more on immigration enforcement -- $18 billion -- than on every other federal law enforcement agencies combined." And as Suzy Khimm documented in the Washington Post, the federal government has already surpassed all of the border security metrics (including miles of fencing, surveillance towers, numbers of border agents and more) required by the 2007 immigration bill blocked by Republicans in Congress. Complaints from the likes of Senator David Vitter (R-LA) that "promises of enforcement never materialize" are simply belied by the facts.
Likely more important than enforcement, both in the near and longer term, is the changing economic and demographic landscape in Mexico. The deep U.S. recession saw jobs for new undocumented workers evaporate, a development reflected in the drop of money ($21 billion in 2011, compared to $24 billion in 2007) sent back to relatives south of the border. (In 2012, Asians and not Hispanics constituted the largest group of new arrivals to the U.S.) In 2010 and 2011, the Mexican economy grew at more than double the pace of the United States. As Simon Rosenberg of the New Democrat Network recently explained:

The Mexican "baby boom" which encouraged so many Mexicans to migrate into the US has ended, and the Mexican economy is producing far more better paying jobs. The birth rate per Mexican woman had fallen from 7.3 in 1960 to almost 2 today. Mexican economic growth is equally significant: by 2010, Mexican GNI per capita had risen to nearly $9,000, up from $3,250 in 1991. Today Mexico is the 13th largest economy in the world, is America's 3rd largest trading partner and 2nd largest export market. If current trends continue, Mexico will be the 5th largest economy in the world by 2050. The result of these developments is that the enormous flow of undocumented immigrants from Mexico into the U.S. we saw in the decade of the 2000s is almost certainly never going to be replicated.

The rising Mexican middle class combined with dramatically slower population growth mean, as Doris Meissner, a commissioner of the Immigration and Naturalization Service under President Bill Clinton and now a fellow at the Migration Policy Institute explained, "We are at a moment when the underlying drivers of what has been persistent, growing illegal immigration for 40 years have shifted." As the Times detailed:

Mexico's population growth has fallen to an annual rate of 1.1 percent in the first decade of this century from 3.2 percent in the 1960s, according to the Migration Policy Institute. The number of people under 15 years old is declining in Mexico, and the number of people ages 15 to 29 will start doing so in the coming years, an important shift given that most illegal immigrants arrive in the United States before age 30.

The result, as the Pew Hispanic Research Center found in late 2011, is that the contracting population of illegal immigrants in the U.S. has been in the country long--and established deeper roots--than most Americans realize:

The Pew Hispanic analysis finds that 35% of unauthorized adult immigrants have resided in the U.S. for 15 years or more; 28% for 10 to 14 years; 22% for 5 to 9 years; and 15% for less than five years. The share that has been in the country at least 15 years has more than doubled since 2000, when about one-in-six (16%) unauthorized adult immigrants had lived here for that duration.

Just as important, Pew found that "that nearly half (46%) of unauthorized adult immigrants today--about 4.7 million people--are parents of minor children."
The meaning of those numbers is unambiguous. Any calls for "self-deportation" or to "send them all back" aren't just completely divorced from reality; such policies would constitute a humanitarian tragedy of epic proportions. Those like Charles Krauthammer who believe that any amnesty before we "build the damn fence" will usher in a new wave of undocumented immigrants from Mexico and Central America are looking at a world that no longer exists. But if Republicans continue to compare the undocumented to "dogs" (Steve King) or "goats" (Trent Lott), or suggest providing free condoms to Mexicans (Mark Kirk) or advocate the construction of an electrified border fence which will "kill you" (Herman Cain), no immigration policy could avoid the backlash from Hispanic voters that kind of GOP xenophobia is certain to produce. And that would spell trouble at the ballot box for years to come from Hispanic voters Pew is calling "an awakened giant:"

To put it another way for divided Republicans, comprehensive immigration reform with a real and fair path to citizenship for today's undocumented isn't just a moral imperative and a political necessity. Now is the time to act. Because while the border isn't--and can never be--100 percent secure, it is already secure enough. That war is essentially over. And if Congress does its job, the people of the United States and Mexico together will have won a great victory for both nations.