Hispanics have been steadily growing as a share of the electorate, from just 1% in 1976 to 10% in 2012.

From The Wall Streeet Journal:

Hispanics have been steadily growing as a share of the electorate, from just 1% in 1976 to 10% in 2012. That year, Republican Mitt Romney performed better with white voters than any presidential candidate in the history of exit polls, but he lost because whites made up just 72% of the electorate and because he did so poorly with minority groups.