WASHINGTON  — Ricardo Campo, a burly and jolly native of El Salvador, and President Barack Obama both have a huge investment in Congress’ attempt to overhaul U.S. immigration laws, to deal with the estimated 11 million people living in the United States illegally.

For Campo, a 21-year-old University of Maryland pre-medical student, his future in the country may depend on it. For President Obama, a sweeping immigration overhaul is central to his legacy, his best hope for legislative success after Congress turned back his push on gun control and a grand bargain on the nation’s finances.

The Senate is considering a bipartisan bill that would make the biggest changes in America’s muddled immigration system since 1986, when Ronald Reagan was president. It would strengthen border security, allow tens of thousands of new high- and low-skilled workers into the country, require employers to check their workers’ legal status and provide an eventual path to citizenship for immigrants now here illegally.