Campaigns temper tone after Colorado shooting, but for how long? In the aftermath of the mass shooting in Aurora, Colo., that left a dozen people dead and dozens more injured, President Obama, Mitt Romney and others have tempered their campaigns in deference to the victims. Romney, speaking at a fundraiser Sunday evening in San Francisco, reflected the somber tone he struck in the hours after the shooting on Friday and acknowledged that Obama was visiting with the families affected on Sunday. He said the message he planned to deliver was different from what he typically offers in such settings. I will note that my remarks today will not be as partisan as normal. Instead I'll talk about my vision for the country in part keeping with the seriousness and the thoughts of the day," Romney told about 250 people gathered at the Fairmont Hotel. We obviously have heavy hearts given a reminder of loss, loss of young minds and youthful voices and soaring spirits, lost senselessly and thoughtlessly. We turn to a power greater than our own to understand the purpose, and if not to understand, then at least to soothe the wounds of those who have been so seriously hurt. Obama, who spent part of the day in Aurora before heading to San Francisco, canceled a grass-roots rally scheduled to be held in Oregon later in the week. "Clearly, the tragic events of last Thursday have changed both the tone and the schedule of events," Obama spokeswoman Jen Psaki told reporters aboard Air Force One on Sunday. We pulled down our event in Portland that was scheduled to happen on Tuesday -- which is a grass-roots event -- for two reasons. One is, of course, the nature of the tragedy and the feeling, while there's not a playbook for this, that given the tone of grassroots events, it was the right step to take. The second reason was that in order to come to Colorado -- which was a big priority for the president, to visit with the families, to do that as soon as it was possible and made sense on both sides -- we had to pull down an event in order to have the resources to do that. The change in tone also affected outside groups. Occupy protesters, who planned to picket a Romney fundraiser in Irvine on Monday, canceled their gathering because of the shooting. The question is: How long does the truce last? In recent weeks, Obama and Romney had been engaged in a bare-knuckles brawl. A lull was already likely because of the impending start of the Olympics. The Aurora tragedy hastened that respite, with both campaigns immediately pulling down ads that had been running in Colorado. But with the party conventions starting in a little more than a month, any truce is expected to be short-lived. "Both candidates have spent most of summer sharpening their talons," said Dan Schnur, director of the Jesse M. Unruh Institute of Politics at USC and a former GOP political operative. It should be interesting to see how quickly a post-Aurora landscape allows them to get back to that type of approach.