Editor's note: Ruben Navarrette Jr. is a CNN.com contributor and a nationally syndicated columnist.
San Diego, California (CNN) -- On the eve of the Nevada caucus, here's some advice to Newt Gingrich: If you still want to draw contrasts with Mitt Romney over immigration, don't toss in your cards. Double down.
Why? Because you're not in Florida anymore.
In the Sunshine State, Gingrich used a controversial and hard-hitting ad to try to paint Mitt Romney as "anti-immigrant." The goal was to weaken the frontrunner's support with Hispanic voters. Despite the fact it made some party loyalists nervous, the label fit. Romney got carried away in the GOP primary, railing against anything resembling "amnesty" in an attempt to offer himself as the preferred candidate for the hostile, intolerant, and frightened. There's a reason that Romney was endorsed by Kansas Secretary of State Kris Kobach, an opportunistic, anti-illegal immigration zealot who helped write many of the constitutionally challenged pieces of legislation clogging up the federal courts in a half dozen states.
Thus, Gingrich had the right strategy. And yet it backfired. Members of the Hispanic establishment in Florida criticized him and demanded he pull the ad. So what went wrong? Ethnicity and geography played a key role in the Florida result.
The overwhelming majority of Hispanic voters in Florida are either Cuban-American or Puerto Rican. They don't have a dog in the immigration fight. While supportive of comprehensive immigration reform and measures like the Dream Act, which would give undocumented students legal status if they go to college or joined the military, these groups aren't directly impacted by the debate. Their lives aren't affected one way or the other by the fact that there are 11 million people in the United States without legal status or that the Obama administration has deported a record 1.2 million people in three years.
Since Puerto Rico is a U.S. commonwealth, Puerto Ricans are U.S. citizens at birth. Meanwhile, Cubans have carte blanche due to the Cuban Adjustment Act, which gives automatic legal status to Cuban immigrants and makes it all but impossible to remove them once they set foot on the U.S. shoreline.
However, Mexican immigrants are not so lucky. Along with Mexican-Americans, they represent more than two-thirds of the U.S. Latino population. For this group, the immigration debate is deeply personal. In a December 2011 study by the Pew Hispanic Center, nearly one quarter (24%) of all Hispanics said they knew someone who had been deported or detained in the past year.
Most Mexicans and Mexican-Americans live in the Southwest. This is the same area of the country where the Republican candidates for president will be spending a lot of time in the next few weeks. After voters go to the polls on Saturday in Nevada (where Hispanics account for 26.5 percent of the population), they'll cast ballots on February 7 in Colorado (20.7 percent) and on February 28 in Arizona (29.6 percent).
These groups of voters are unlikely to do what the Florida voters did and simply shrug off the charge that Romney is anti-immigrant. They're more likely to take umbrage at some of the positions that Romney has taken -- for instance, his opposition to the Dream Act as presently written. The bill has the support of 90 percent of Hispanics. So while Romney won a solid majority of the Hispanic vote in Florida, 54 percent to 29 percent for Gingrich, the challenger should not be discouraged. Instead, Gingrich should dust off the "anti-immigrant" ad he used against Romney there and air it again in Colorado and Arizona. He should reopen the immigration debate and force Romney to defend himself. The presumptive GOP nominee needs to explain whether he sees immigrants -- legal and illegal -- as a net positive or negative to the United States.
Romney also needs to take responsibility for a massive flip-flop: Having spent months attacking his opponents for supporting proposals that would allow the undocumented to pay in-state university tuition or work legally in the United States, Romney told a roomful of Hispanic conservatives in Florida that he supports giving illegal immigrants "temporary worker permits."
Under the Romney plan, the undocumented could remain in the U.S. to work for a certain period of time. After the time is up, the immigrants would hopefully "self-deport" but the government wouldn't make them leave. It's the very thing that the old Romney would have derided as a form of amnesty -- that is, before he discovered Florida's sizable Hispanic population and felt the urge to pander to it.
Romney is vulnerable with Hispanics. Gingrich needs to use the primaries and caucuses in the Southwest to go back on the offensive. The immigration issue lets him do that. Gingrich has to stop whining about what he calls Romney's stunning level of dishonesty. What did he expect from a fellow politician?
Instead, Gingrich needs to start making the case to Republican voters that the road to the White House goes right through the U.S Hispanic community and that he alone can lead the way.
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The opinions expressed in this commentary are solely those of Ruben Navarrette Jr.