Failing to overhaul the nation's immigration system, currently a back burner issue for Congress and President Barack Obama, could play a pivotal role in key mid-term election in November, according to a new study on Latino voting patterns.

The report by America's Voice, which supports comprehensive new immigration policies, says revising the laws is the defining issue for Latino voters. The report says that progress -- or the lack thereof -- in revamping immigration laws and regulations could affect as many as 40 congressional races in areas with sizable Latino populations, including the reelection bids of Senate Majority Leader Harry Reid, D-Nev., and Sen. John McCain, R-Ariz., just two years ago his party's presidential candidate.

``Immigration reform is a litmus test in the Latino community,'' Eliseo Medina, the president of the Service Employees International Union, said during a conference call about the study. ``To us, this is a policy issue, but it is also an issue about respect.''

The study says that Obama and Democrats who campaigned in 2008 on the promise of revamping immigration laws benefited from a 54 percent growth in registered Latino voters between 2000 and 2008.

Obama received 75 percent of the Latino vote in 2008.

Since the election, several Latino organizations and leaders have expressed frustration with Obama and congressional Democrats for not aggressively pushing a comprehensive immigration bill.

Latino leaders and groups are similarly frustrated with Republicans. They feel that the GOP is promoting and campaigning on an anti-immigration agenda.