(AP) – Both sides are squaring off over a sweeping immigration bill on the opening day of a Senate committee hearing.

The top Republican on the Senate Judiciary Committee is Chuck Grassley of Iowa. In opening remarks, Grassley insists the landmark legislation backed by President Barack Obama does little more than repeat mistakes of the past.

A lead author of the bill is Democrat Chuck Schumer of New York. Schumer counters that it represents the country’s best hope for immigration reform.

The legislation would toughen border security, remake legal immigration, block employers from hiring anyone in the U.S. illegally, and create a path to citizenship for the 11 million already in the U.S.