President Obama, in a major speech on immigration in the U.S.-Mexico border city of El Paso, Texas today, lambasted Republicans for refusing to join him and Democrats in a major push on comprehensive immigration reform, including a sweeping legalization program that Republicans have denounced for years as an unconscionable “amnesty.”

The speech was widely viewed as an effort by Obama to win back disaffected Latino voters, whose 2-1 support for Obama in 2008 helped him carry key Southwestern swing states as well as Florida and Virginia.

The latest Gallup poll has Obama’s approval rating with Latinos at 54%, tying a record low. His numbers are even lower among Spanish-speaking Latinos, including naturalized U.S. citizens, who tend to be especially focused on immigration questions. And even more troubling for the president, just 42% of Latinos think Obama should be re-elected.

Obama’s speech — one of his most partisan in recent months — placed all the blame for the lack of progress on immigration reform squarely on Republicans, whom he accused of “moving the goalposts” on border security in order to delay consideration of other badly needed items on the immigration reform agenda, including passage of the so-called DREAM Act, which would create a path to citizenship for illegal immigrants who immigrated to the U.S. as minors. In his speech, Obama pledged to support the DREAM Act again this year.

“We’ve done everything they’ve asked us to do,” Obama said, noting that the proposed 70-mile border fence is largely finished. “But even if we built a moat at the border, and put alligators in it,” Obama joked, Republicans “still wouldn’t be satisfied” that the border is “secure.”

The speech, delivered to a largely enthusiastic crowd at Chamizal National Memorial Park, is likely to cause considerable uproar among Republicans, who see progress in border security as just one element in the country’s immigration enforcement package. Obama made no mention, for example, of efforts to tighten enforcement at the workplace through the introduction of a database verification system that could weaken the “job magnet” for illegal immigration.

Also missing from the speech was any mention of huge problems that still exist in tracking people who enter the country legally on tourist or work visas but refuse to go home when their visas expire — a group that represents an estimated 40% of the 11 million illegal immigrants currently in the country. A recent U.S. General Accounting Office report found issues with the current tracking system for these “visa overstayers,” known as VISIT, thanks in part to a lack of congressional funding, as well as bureaucratic turf competition between the State Department and the Department of Homeland Security over how to implement the program.

Republicans are also likely to object to Obama’s seeming attempt to blur the distinction between legal and illegal immigration by highlighting the potential of foreign-born engineers and scientists who enter the country on work visas and who many consider vital to restoring American competitiveness at a time of growing competition from China and other nations.

Republicans, including many who oppose illegal immigration and want to see enforcement tightened, have been in the forefront of promoting expanded visas for high-skill workers, many of whom are Asian and lean GOP. It’s the Democrats who have traditionally focused on the plight of low-skill workers by promoting green cards to those who’ve arrived in the U.S. illegally, primarily Mexicans, who still tend to favor Democrats in national elections.

Prior to Obama’s latest speech, there was some hope that the two parties might find a way to pass a compromise immigration bill in the small legislative window that still exists before the onset of the 2012 presidential campaign. But rather than suggest a true path to compromise, Obama clearly prefers more finger-pointing and posturing — in the hopes that blaming the GOP will rally Latinos to his side.

Will it work? Even some long-time Democrats are worried that it may not this time. Obama has promised progress on immigration reform for over two years, and he largely squandered his best chance at forging a deal in the early months of his presidency — and many Latinos know it. With Latino unemployment at 13%, and no improvement in sight, America’s fastest growing voter group is starting to take a fresh look at the GOP. Obama’s latest PR gambit isn’t likely to change that.

Stewart J. Lawrence is a Washington, D.C.-based public policy analyst who writes frequently on immigration and Latino affairs. He is also founder and managing director of Puentes & Associates, Inc., a bilingual survey research and communications firm.