As the fastest-growing population group in the U.S. during the last decade, Hispanics seemed poised to have a huge impact on the 2012 presidential and congressional campaigns.

Why then, political experts and demographers wondered, did the number of Hispanic voters decline significantly between 2009 and 2010?

According to data from the U.S. Census Bureau’s Current Population Survey, the number of Hispanic registered voters fell from 11.6 million in 2008 — a presidential election year — to 10.9 million in 2010, when congressional races led the ballot in many states.

Experts had expected 11 million to 12 million Hispanic voters to visit the polls in November. But the survey cast serious doubts on that.

Some wondered whether the economy had forced Hispanics to move to find work. Others said the drop was strictly cyclical.

Although voter registration typically slips in nonpresidential years, some experts say the scope of the 2010 declines were completely unexpected at a time when the overall Hispanic population in the U.S. continued to soar.

From 2000-10, the number of Hispanics in the U.S. jumped from 35.3 million to 50.5 million, a growth rate of 43%. Hispanics made up 16% of the U.S. population in 2010.

Antonio Gonzalez, president of the William C. Velasquez Institute and the Southwest Voter Registration Education Project, blamed the recession for the decline in registered voters, especially the housing bubble and foreclosure crisis, which forced many Hispanics to move to find work.