In this Friday, June 29, 2012 photo, Carissa Valdez, left, a volunteer for President Barack Obama's reelection campaign, listens to Ruben Gallardo, who she registers to vote, as a group of volunteers work to register new voters as they canvass a heavily Latino neighborhood in Phoenix. Across the country both political parties have been courting the Latino vote, the nation's fastest-growing minority group. (AP Photo/Ross D. Franklin)

In this Friday, June 29, 2012 photo, volunteer for President Barack Obama's reelection campaign, Vergie Morris, left, registers Valentin Navarro to vote as volunteers register new voters at a table set up in front of campaign headquarters at a local shopping plaza in Phoenix. Across the country both political parties have been courting the Latino vote, the nation's fastest-growing minority group.(AP Photo/Ross D. Franklin)

In this Friday, June 29, 2012 photo, Brian Conklin, left, a regional campaign director for President Barack Obama's reelection campaign, briefs volunteers Caroline Alcaida, right, and Sheila Morris before they head out of the campaign office to register new voters as they canvass in a heavily Latino neighborhood in Phoenix. Across the country, both political parties have been courting the Latino vote, the nation's fastest-growing minority group. (AP Photo/Ross D. Franklin)

In this Friday, June 29, 2012 photo, Brian Conklin, far right, a regional campaign director for the reelection of President Barack Obama, briefs volunteers about registering new voters prior to them canvassing a heavily Latino neighborhood in Phoenix. Across the country both political parties have been courting the Latino vote, the nation's fastest-growing minority group.(AP Photo/Ross D. Franklin)

In this Friday, June 29, 2012 photo, Brian Conklin, a regional campaign director for President Barack Obama's reelection, gets clipboards ready before campaign volunteers arrive to register new voters prior to canvassing a neighborhood in Phoenix. Across the country both political parties have been courting the Latino vote, especially for the presidential election, the nation's fastest-growing minority group.(AP Photo/Ross D. Franklin)

In this Friday, June 29, 2012 photo, Hector Acuna, a volunteer for President Barack Obama's reelection campaign, joins about a dozen others as they are briefed on how to register new voters prior to canvassing in a heavily Latino neighborhood in Phoenix. Across the country both political parties have been courting the Latino vote, the nation's fastest-growing minority group. (AP Photo/Ross D. Franklin)

In this Friday, June 29, 2012 photo, volunteers for President Barack Obama's reelection campaign get fliers ready as they work to register new voters prior to canvassing a heavily Latino neighborhood in Phoenix. Across the country both political parties have been courting the Latino vote, the nation's fastest-growing minority group.(AP Photo/Ross D. Franklin)