WASHINGTON — When Senator Tim Kaine, Democrat of Virginia, took the Senate floor on Tuesday to deliver a speech in support of an immigration overhaul bill, he did it in a way no senator had done before: entirely in Spanish.

“We are going to have hours upon hours of debate about this on the floor of the Senate, and taking 15 minutes to explain the bill in Spanish just seemed like a good idea,” Mr. Kaine said. “Latinos have so much invested in the outcome of the bill, people ought to know what the bill is about.”

According to records from the Senate Library, Mr. Kaine was the first senator to give a speech all in Spanish on the Senate floor. Senator James M. Inhofe, Republican of Oklahoma, spoke Spanish in brief statements on the floor in 2003 and 2005, and former Senator Mel Martinez, Republican of Florida, did the same in 2005.