CHARLOTTE, N.C.

Four years later Democrats have gathered again, this time in support of a president who carries the power and the burden of incumbency, both in evidence as the opening gavel is struck at the Democratic National Convention.

President Barack Obama demonstrated the power Monday in a convention eve visit to hurricane-stricken lands in Louisiana, offering aid and empathy. His burden is a ragged economy that is at the core of the hotly competitive contest with Republican Mitt Romney.

Michelle Obama’s speech tonight is an early highlight of a three-day schedule that has drawn thousands of delegates to a state Obama narrowly carried in 2008. Although Obama no longer is the fresh-faced newbie who leveraged a short Senate career into an audacious run for the nation’s highest office, he still can excite partisans, and Democrats were counting on massive numbers to pack a stadium for his speech later in the week.

If hurricanes have no politics, the aftermath does. Obama’s visit to stricken St. John the Baptist Parish outside New Orleans after a spirited Labor Day rally in battleground Ohio demonstrated, if in muted form, the partisan divide that cleaves the presidential campaign.

Obama emphasized the government’s determination to lend a strong helping hand. Romney focused on neighbor helping neighbor in his visit days earlier, even though both support a mix of emergency aid from the taxpayer and volunteerism in response to natural disasters.

“We’re here to help,” Obama told residents during a brief tour Monday, going from lawn to lawn in a neighborhood of brick homes and front yards loaded with soggy but orderly piles of debris, the floodwaters receded. He told another family of the steps officials were taking to address the damage, adding, “I promise you that now that I’ve been here, they’re going to make sure that they do it right.”

On convention eve, Democrats released a party platform for ratification today that echoes Obama’s call for higher taxes on the wealthy and reflects his shift on gay marriage by supporting it explicitly.

In a nod to dissenters on gay marriage, the platform expresses support for “the freedom of churches and religious entities to decide how to administer marriage as a religious sacrament without government interference.”

As with the deeply conservative Republican platform, not all of which Romney endorses, nothing binds Obama to the specifics of the party’s manifesto.

The president rallies in Virginia today before joining the convention a day later. With flourishes but no suspense, Democrats will march through the roll call of states renominating Obama for president and Joe Biden for vice president on Wednesday.

That’s also when the convention hears from Bill Clinton, whose 1990s presidency is being trumpeted by Democrats as the last great period of economic growth and balanced budgets — a further redemption of sorts, at least from his party, for a leader who survived impeachment over sexual scandal.

In a USA Today interview, Obama accused Republicans of building their campaign around a “fictional Barack Obama” by wholly misrepresenting his positions and words. He singled out Romney’s claim, widely debunked, that the Obama administration stripped a work requirement out of federal welfare laws.

His convention behind him, Romney relaxed at his lakeside home in New Hampshire with his family as Obama and Biden sought to motivate union voters to support them in difficult economic times. Romney took a midmorning boat ride, pulling up to a dock to fuel up his 29-foot Sea Ray and pick up a jet ski that had been in for repairs.

In his Labor Day statement, Romney said, “For far too many Americans, today is another day of worrying when their next paycheck will come.”

The Republican convention last week heard testimonials from a colleague of Romney at Bain Capital and from the founder of Staples, the office supply chain that grew from the private-equity firm’s investments. Democrats, focused on enterprises that closed or moved overseas after Romney’s firm got involved, are giving speaking time to workers from Baincontrolled companies who will tell the other side of the story.

Campaigning on Saturday in Cincinnati, Romney had likened Obama to a football coach with a record of 0 and 23 million, a reference to the number of unemployed and underemployed Americans.

Obama offered a play-byplay rebuttal 48 hours later.

“On first down he hikes taxes by nearly $2,000 on the average family with kids in order to pay for massive tax cuts for multimillionaires,” Obama said in his Toledo rally. “Sounds like unnecessary roughness to me.

“On second down he calls an audible and undoes reforms that are there to prevent another financial crisis and bank bailout. …

“And then on third down, he calls for a hail Mary, ending Medicare as we know it by giving seniors a voucher that leaves them to pay any additional cost out of their pockets. But there’s a flag on the play: Loss of up to an additional $6,400 a year for the same benefits you get now.”

Romney denies that his plan to help the economy and reduce federal deficits will result in higher taxes for the middle class. But he has yet to provide enough detail to refute the claim. Obama’s assertion rests on a study by the nonpartisan Tax Policy Center.