URBANDALE, Iowa — Setting out on a campaign trek headed toward his nomination at the Democratic National Convention this week, President Obama on Saturday sharpened the theme his team hopes will recapture the momentum and energy from four years ago: “Forward.”

In a speech with cutting jokes, Obama cast his Republican rival as a product of another time who is pushing policy “retreads” that have been tried and failed. And he ripped the GOP convention that wrapped on Thursday as a “rerun.”

“We’d seen it before. You might as well have watched it on a black-and-white TV,” Obama told an estimated 10,000 people at a farm museum in Urbandale.

The president unveiled his “Forward” slogan when he launched his campaign in May, but it has hardly caught fire the way “Hope” and “Change” did four years ago. As he zips through swing states on his way to the convention in Charlotte, N.C., Obama seems to be punching up the theme, weaving it into his policy arguments with the aim of reclaiming his status as the candidate of the next generation.

Obama’s challenge is a harder one this time around. Mitt Romney, while hardly a new political figure, is not the well-established, white-haired rival Obama had in Arizona’s Sen. John McCain. The addition of Wisconsin’s Rep. Paul D. Ryan, a 42-year-old father with small children, added youth to the ticket. Romney and Ryan, too, have tried to play up their youthful side. As he accepted his party’s nomination on Thursday, Romney joked that he still preferred his iPod playlist to Ryan’s Led Zeppelin.

For his part, Obama offered to recap the Republican convention “if you didn’t DVR it.”

Romney stuck to his jobs message on Saturday as he campaigned in Cincinnati and in Jacksonville, Fla., where Ryan joined him. The former Massachusetts governor said Obama had not done enough to encourage new businesses, using a sports metaphor on college football’s opening weekend.

“We are at a 30-year low in startups and new businesses, and that’s where jobs are created,” Romney said at an outdoor plaza in Jacksonville. “He said he’d measure success by whether people were able to find new jobs. We have 23 million Americans out of work, or dropped out of the workforce, or can’t find full-time work.”

“Look, if there’s a coach whose record is zero and 23 million, you get rid of him and get someone new,” Romney said to huge cheers. “I don’t like the way the game is going under this president.”

Romney, who noted that he had seen a report Saturday showing a drop in income for middle-class families, has promised to create 12 million jobs through tax cuts and less regulation. “You’re going to see more jobs and more take-home pay, not just because you want it, but because you deserve it,” he said.

The Republican candidate plans to take a break from campaigning over Labor Day weekend with a stay at his vacation home in Wolfeboro, N.H. Aides said Saturday that Romney would spend much of next week preparing for the fall presidential debates with key advisors, including Ohio Sen. Rob Portman.

As he traveled Saturday, Obama was prepping for the week ahead. A spokeswoman said the president would be working on his acceptance speech while aboard Air Force One.

Obama said the Thursday night speech would offer “a better path forward,” and pointed at his positions on taxes, energy and healthcare as a glimpse. Notably, although he ripped Romney as not unveiling a “single new idea” in Tampa, Fla., Obama, too, used familiar proposals to draw a contrast with his opponent.

The president noted that Romney did not mention Afghanistan in his acceptance speech and offered no new plan to end that conflict. He criticized Romney’s proposals to cut tax rates and Ryan’s 2011 plan to overhaul Medicare. “Despite all the challenges that we face in this new century, what they offered over those three days was more often than not an agenda that was better suited for the last century,” he said.

Obama made two stops in Iowa, his 18th and 19th events in the state this year. The lavish attention is a reflection of the importance of this battleground and the fierce fight underway on the ground.

Iowa is something of a linchpin in Obama’s “small state” strategy, which would allow him to lose Ohio, Florida and Virginia if he locks up smaller swing states, including New Hampshire.

Obama won Iowa by 9 percentage points in 2008. Polls show the current race essentially tied.

kathleen.hennessey@latimes.com

maeve.reston@latimes.com

Hennessey reported from Urbandale and Sioux City, Iowa; Reston reported from Cincinnati and Jacksonville, Fla.