WASHINGTON — Politicians of all stripes are bound to be haunted by Rep. Gabrielle Giffords’ warning, 10 months before she was shot, to cool the rhetoric.

It’s been a year or more of raw politics, with anger spilling over on both sides and gun-related metaphors coming loosely from the lips of some candidates and activists. Giffords, a figurative target of the right, on Saturday became the actual target of a gunman who shot her through the head and killed at least five others. She was critically wounded.

The gunman’s motive is not known.

But in Pima County, Ariz., Sheriff Clarence Dupnik suggested "all this vitriol" in recent political discourse might be connected to Saturday’s shootings. "This may be free speech," he told reporters, "but it’s not without consequences."

Whatever the motive, the toxic tone of the national debate is certain to draw greater scrutiny.

"We do know that politics has become too personal, too nasty and perhaps too dangerous," said Jonathan Cowan, president of the centrist Democratic group Third Way. "Perhaps out of this senseless act some sense can return to our public discourse."

In the aftermath of the rampage, the House’s newly installed Republican leaders postponed Wednesday’s scheduled vote to repeal the new health care law, the issue at the center of the harshest criticisms of Giffords and many other Democrats for the past two years. Lawmakers from both parties were deeply shaken.

Many lawmakers, especially Democrats, felt the 2009-2010 debate over health care sometimes got out of hand. It began with emotional town hall meetings in the summer of 2009, when some critics warned of government "death panels."

Giffords, 40, was among lawmakers who reported 42 threats or acts or vandalism in the first three months of 2010, a big increase over the previous year, law enforcement officers said. Nearly all the threats dealt with the massive health care bill that Giffords and other Democrats enacted over fierce Republican opposition.

In March, someone kicked in or shot out a glass door and side window at Giffords’ office in Tucson, a few hours after the House passed the health care measure with her help.

Giffords also was among about 20 Democrats opposed in last fall’s elections by Sarah Palin, the 2008 GOP vice presidential nominee. Palin’s Facebook page in March posted a U.S. map with the cross-hairs of a gun scope imposed over each of the 20 Democrats’ districts. Gun imagery appeared in various ways in the campaign, often not connected at all with gun rights.

"We’re on Sarah Palin’s targeted list," Giffords said at the time. "The way that she has it depicted has the crosshairs of a gun sight over our district. When people do that, they’ve got to realize there are consequences to that action."

Palin’s Facebook page had the following comment in the hours after the shooting:

"My sincere condolences are offered to the family of Rep. Gabrielle Giffords and the other victims of today’s tragic shooting in Arizona."

Ferocious comments, and even occasional violence, certainly animate American politics from time to time; witness the bloody drive for racial equality and desegregation, and the antiwar protests, of the 20th century. The question now, and again, is how much is too much, and how hot is too hot, in political discourse.

"Anger and hate fuel reactions," said Democratic Rep. Raul Grijalva, whose Arizona district also includes parts of Tucson. He said he was not assessing blame, and Saturday’s shootings might be the work of "a single nut." But he said the nation must assess the fallout of "an atmosphere where the political discourse is about hate, anger and bitterness ."

The Jewish Council for Public Affairs said in a statement: "While we do not know the motives for today’s attack, we do know that it cannot be viewed apart from the climate of violence and the degradation of civil society that are anathema to democracy."

The suspected shooter, Jared Loughner, complained about the government in online diatribes that also spoke in scattered ways of currency, terrorism and "mind control." But what might have driven him to violence has not been established.

"We don’t yet know what provoked this unspeakable act," President Barack Obama said from the White House. "We are going to get to the bottom of this."

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EDITOR’S NOTE — Charles Babington has covered politics from Washington since 1987.