(CBS News) LAS VEGAS- At the end of what he called a "tough day," on which it was learned that four American personnel were killed in Libya, including the U.S. ambassador, President Obama used a campaign rally to talk tough, vowing to "bring their killers to justice." His audience of some 8,000 supporters gave him a thunderous cheer.
"And we want to send a message all around the world to anybody that would do us harm: No act of violence will shake the resolve of the United States of America," he declared.
Standing behind a lectern bearing the presidential seal instead of a campaign placard, Mr. Obama said the U.S. will not be deterred, because "the world needs us. We are the one indispensable power in the world."
He later said that the U.S. will be "relentless in our pursuit of those who attacked us yesterday."
Just before his rally, President Obama also cited the killings in Libya during an online conference call with campaign volunteers. He spoke of his visit to the State Department earlier in the day "to comfort some of the friends and coworkers of the folks who've fallen."
"Obviously our hearts are broken for their families, but I wanted to encourage those folks at the State Department to understand they're making a difference," Obama said.
He said the sacrifices that American troops and diplomats make are "obviously very different" from those of campaign volunteers, but, he said, "you guys are Americans who sense that you can do better than you're doing and you're willing to put it on the line."
Despite the grievous news from Libya that American Ambassador Chris Stevens and three other personnel were killed during an assault on the U.S. Consulate in Benghazi, President Obama went ahead with a two-day campaign swing to two key swing states: Nevada and Colorado.
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Defending the decision, Obama Campaign press secretary Jen Psaki told reporters that it would not be "a day of politics as usual." She said President Obama's remarks at the rally would reflect "the tone" of what happened in Libya.
That was true of the top of Pres. Obama's remarks, but the rest of his speech at an exhibition hall well north of the Las Vegas strip, contained the familiar boilerplate that makes up his standard stump speech.
It included his charge that Mitt Romney would cut taxes for the very rich and end up having to raise taxes on the middle class. It's a charge Romney vehemently denies.
"I refuse to ask middle class families like yours to pay more, so millionaires and billionaires can pay less," said the president.
He also repeated his veiled reference to GOP vice presidential candidate Paul Ryan, saying that when we hear folks say this nation is in decline, "they are dead wrong."
He vowed that he "will never turn Medicare into a voucher," which he says the Romney/Ryan Administration would do. And he said "we'll keep the promise of Social Security," "not like turning it over to Wall Street like a stack of poker chips," using a metaphor befitting his presence in the gambling center of America.
This was President Obama's seventh visit this year to Nevada, a state with only 6 electoral votes, but a state he won in 2008 and wants to keep Mitt Romney from winning in November.
From Las Vegas, President Obama headed to another swing state this year that he won in 2008: Colorado. He has a campaign rally in Golden on Thursday morning before returning to Washington in the evening.