The key difference between the immigration proposal released last week by eight U.S. Senators and another by President Barack Obama is whether border security must happen before immigration policy changes take place.

"The Senate version says before we can start legalizing the undocumented population we have to secure the border. The Obama dministration proposal does not include that enforcement trigger," said Judith Gans, Immigration Policy Program manager with the Udall Center for Studies in Public Policy at the University of Arizona.

The policies differ in other ways, as well, including what border security looks like, and how it is accomplished.

"It's not really clear what we mean by 'securing the border,'" Gans said. "Some people talk about fencing the whole border, some people talk about apprehension metrics."

Gans has studied immigration policy for years, and said she's more optimistic these new immigration proposals have a chance at passing than past versions. The last election pundits and politicians focused on Latino voters.

Some of them are supporting the proposals to change the nation's laws and that "does indicate a real sea change in politics," Gans said.