But the shifting political crosscurrents in the immigration debate are making it increasingly difficult to predict how Hispanic voters will behave in the upcoming midterm elections.

Hispanics have been frustrated by President Barack Obama and congressional Democrats’ unfulfilled promises to reform the nation’s immigration system. But they’ve also been alienated by Republicans, who have taken a harsher stand on illegal immigration this year, including Arizona’s new law at the heart of the immigration battle.

“It’s translating into a sense of anger and frustration among the Latino community, and one of the strongest motivators for voters is anger,” said Arturo Vargas, who heads the National Association of Latino Elected and Appointed Officials in Los Angeles.

But while registered Latino voters favor Democrats over Republicans by a 3-to-1 margin, a poll this week found that they are less enthusiastic about the upcoming elections than the overall electorate.

Only a third of all Latino registered voters said they have given this year’s election “quite a lot” of thought, the Pew Hispanic Center poll found,  compared with half of all registered voters.

And 51 percent of Latino voters said they are absolutely certain they will vote in November, compared with 70 percent of all registered voters.

“It looks like Latinos are less motivated than all registered voters,” said Mark Hugo Lopez, associate director of the Pew Hispanic Center.

Yet Vargas contends Hispanics are deeply engaged this election. From his observations, Vargas says Latino voters are closely monitoring every development of the immigration debate, from the recent push by Democrats to pass the DREAM Act to the legal fight over Arizona’s SB 1070.

The law, which sparked protests and boycotts from Hispanic activists, makes it a state crime to be in the country illegally and requires police to check the immigration status of individuals suspected of being illegal immigrants — though those contentious provisions were temporarily blocked by a federal judge after the Justice Department intervened.

Despite general frustration at the slow pace of immigration reform, Hispanics cheered the decision by the Obama administration to fight the Arizona immigration law in court.

And a poll this week suggests a last-minute push by Senate Democrats to pass the DREAM Act on Sept. 22 appeared to give the party a slight bump in the polls among Hispanics.

While the effort to give young, illegal immigrants a path to legalization was blocked by Republicans, a Latino Decisions poll  showed 35 percent of Hispanics think Democrats are working to pass immigration reform. That was up from 26 percent of Hispanics polled just days before the DREAM Act vote.

“It’s hard for me to believe that only 30 percent is following the election closely. It seems incongruous to what we’re seeing out in the community,” Vargas said. “It’s in the news every single night, and I think these people are following these developments very closely.”

Still, Hispanic activists aren’t leaving anything to chance.

The NALEO Educational Fund is identifying and contacting a quarter-million “low-propensity” Latino voters in five states with significant Latino populations — Texas, California, Arizona, New York and Florida — to get them to the polls. And Mi Familia Vota’s get-out-the-vote campaign signed up more than 20,000 Latinos to Arizona’s permanent early-voter list.

A depressed Latino voter turnout could spell trouble for Democratic candidates in several high-stakes races this year, particularly in California, where Latinos make up nearly a fifth of the electorate.

A Reuters/Ipsos poll on Wednesday had incumbent Democratic Sen. Barbara Boxer leading GOP challenger Carly Fiorina by just 4 points. And in Nevada — another state with a large Hispanic population — Senate Majority Leader Harry Reid and Republican nominee Sharon Angle are running neck and neck. In a new campaign mailer, Angle hit Reid over the immigration issue, calling him “an illegal alien’s best friend.”