Hillary’s aides were grumbling last week that Obama had no rationale to offer but himself.

Perhaps that was true when he started. People usually run for president because somebody tells them they should and then graft on the reasons afterward. But on Thursday, Obama’s vague optimism and smooth-jazz modernity came together in a spectacular fusion with the deep yearning of Democrats who have suffered through heartbreaking losses in the last two elections with uninspiring candidates.

Often unable to surf the electricity he sparked over the last year, Obama has now put on his laurel wreath and dropped his languid pose, tapping directly into what he calls the “fire burning” across the country  the dream of a cool, smart, elegant, reasonable, literary, witty, decent “West Wing” sort of president who won’t bankrupt us or endanger us or co-opt our rights or put a black hood on the Constitution.

“I want to go before the world and say, America’s back,” he told cheering Democrats in Milford, N.H., adding: “We are one nation. We are one people. And our time for change has come.”

Even though Obama was wooing the young demographic so coveted by Hollywood, he took a page from J.F.K. and avoided the casual look last week. There were no jeans or snow boots. Just dark suits, stylish ties and dress shoes.

By the time she got to New Hampshire, Hillary was reduced to urging voters not to buy into “false hopes.”

At a hangar in Nashua, with chatty Bill and chatless Chelsea, Hillary tried to purloin more of the Obama message. Besides saying the word “change” as often as possible, she said she was particularly reaching out to young people to help them “reclaim the future.” She claimed that she disliked the red state, blue state terminology  “We are one country,” she said, echoing Obama  even as she added that she should be the nominee because she’s the best one “to withstand the Republican attack machine.”