Washington ? The number of serious threats, including death threats, against members of Congress jumped in the past three months during the heated debate over the new health care law.

House Speaker Nancy Pelosi, the target of phone attacks that brought an arrest this week, said in an interview Thursday the 24/7 nature of news and commentary can provoke an emotional response that leads people to act before they can check their own behavior or the truth of what they’ve heard.

“We all have a responsibility, when we make our appeal to the public, to understand that sometimes these fall on ears of people who can’t cope with that kind of information,” she said.

Senate Sergeant-at-Arms Terrance W. Gainer, who monitors security in the House and the Senate, said lawmakers reported 42 incidents in the first three months of this year, nearly three times the 15 cases during the same time last year.

That period coincided with debate and eventual passage of health care overhaul legislation, one of the most partisan and divisive issues Congress has taken up since the civil rights battles a half-century ago. Democrats and a few Republicans reported receiving threats against them or their families.

But threats against elected officials are as old as the nation itself.

Ray Smock, who served as historian of the House from 1983 to 1995, recalled that in the 1960s, supporters of civil rights legislation “got all kinds of racist mail.”

“Every Ku Klux Klanner and other white supremacist groups were making death threats,” Smock said.

But he said the anger has taken on new dimensions in the past two decades with the advent of 24-hour cable news and the expansion of political talk shows. “I do think that people who are sort of on the ragged edge can get inflamed by all this rhetoric,” said Smock, who now heads the Robert C. Byrd Center for Legislative Studies at Shepherd University in West Virginia.

More potentially heated debates are brewing between now and the November elections, including the nomination of a replacement for retiring Supreme Court Justice John Paul Stevens.

So far, nearly all of the threats appear linked to opponents of health care legislation, Gainer said. At least three people have been arrested for threatening members of Congress. Capitol police are working with the FBI and other law enforcement offices to follow up on serious threats and ensure that lawmakers’ offices are safe.