Flying into New Orleans, Obama traveled by motorcade to nearby St. John the Baptist Parish, one of the hardest-hit communities, to meet federal, state and local officials and assess the disaster response before surveying the area.
As he arrived on hot, sunny day, Obama saw evidence of the storm's fury - twisted road signs, toppled trees and pools of water beside the road.
The White House has taken pains to depict Obama as deeply engaged in the government's handling of Isaac and its aftermath. His Republican predecessor, George W. Bush, was heavily criticized for the sluggish federal response to Hurricane Katrina, which devastated New Orleans in 2005.
Being cast in the role of consoler-in-chief could have political benefits for Obama, who is locked in a tight race with Romney and will accept his party's nomination in a prime-time speech on Thursday night in Charlotte, North Carolina. The convention begins on Tuesday.
Isaac was the first hurricane to strike the United States this year, hitting New Orleans almost exactly seven years after Katrina devastated the city, causing an estimated 1,800 deaths.
But Isaac was a much weaker storm. It was blamed for six deaths in Louisiana and two in neighboring Mississippi, and both states suffered from widespread flooding.
MORE THAN 100,000 WITHOUT POWER
Even as the fading remnants of Isaac moved east, about 125,000 people remained without power in Louisiana, the governor's office said. With floodwaters not yet receded in some areas, about 2,600 people remained in emergency shelters. Obama has declared disasters in Louisiana and Mississippi.
Isaac's passage through Gulf of Mexico last week forced cancellation of one day of the Republican convention in Tampa, Florida, and took some attention away from it as the storm barreled toward landfall farther north.
Obama, staying away from the region while emergency officials were occupied with the height of the crisis, waited until Monday for his visit. He went ahead with a Labor Day rally with union workers in Ohio but freed up time in his campaign schedule by scrapping a second event in the political battleground state.
Romney, who has struggled to show that he can connect with ordinary Americans, wasted little time before detouring to the disaster zone the day after his convention.
The White House sought to play down any political implications and highlighted the fact that Louisiana's Republican governor, Bobby Jindal, accompanied both of the men.
But White House spokesman Jay Carney echoed Democrats who have pointed out that Romney's vice presidential running mate, congressional fiscal hawk, Paul Ryan, had earlier proposed sharp cuts in disaster relief spending.
"Disasters are apolitical," Carney told reporters on Air Force One. But he added, "Last year there was an effort to underfund the money that's used to provide relief to Americans when they've been hit by disasters. That effort was led by Congressman Paul Ryan."
Meantime, oil operations that had been interrupted along the Gulf Coast were slowly coming back on line.
The U.S. Energy Department said the Exxon Mobil Corp's joint-venture 192,500 barrel per day (bpd) Chalmette, Louisiana, refinery was restarting on Monday after being shut last week because of Isaac.
The Energy Department also said Exxon's 502,500 bpd Baton Rouge refinery has returned to a normal production level after reducing throughput during Isaac's approach to and passage across Louisiana.
Only Phillips 66's 247,000 bpd refinery in Alliance, Louisiana, remained shut down on Monday due to flooding and power loss from the storm, the agency said.
