ST LOUIS (Reuters) - White House hopeful John McCain and running mate Sarah Palin hit the campaign trail as a team on Saturday, seeking to build on the momentum of her surprise addition to the Republican ticket even as Hurricane Gustav threatened to overshadow next week's party convention.
The Arizona senator and Alaska governor will fly to Mississippi on Sunday to view preparations for the hurricane, adding a last-minute trip in an effort to contrast their would-be administration with President George W. Bush's slow response to Hurricane Katrina three years ago.
The two candidates will visit a storm command center in Jackson, a spokeswoman said.
Forecasts showed Gustav could come ashore as a powerful storm in Louisiana by late Monday or early Tuesday.
McCain told a rally in Washington, Pennsylvania, he was keeping the people in the Gulf Coast in his prayers and said in a taped interview that the convention could be postponed.
"It just wouldn't be appropriate to have a festive occasion while a near tragedy or a terrible challenge is presented in the form of a natural disaster," he told Fox News.
The rally marked McCain and Palin's second full day in public as a political ticket. People shouted, "Sarah, Sarah!" as the Alaska governor took the stage with McCain, whose vice presidential pick on Friday ignited fundraising and drew Democratic scorn.
McCain and Palin will be nominated officially at the convention in St. Paul, Minnesota. Bush is scheduled to speak there on Monday evening, but White House spokeswoman Dana Perino said the administration was making contingency plans that could include an address via satellite instead.
"We continue to track the path of the storm and there is no scheduling change to speak of yet," she told reporters.
Republican convention organizers said they were also monitoring the storm and considering contingencies.
Democratic nominee Barack Obama, campaigning in Ohio, spoke by phone with Louisiana's governor and the mayor of New Orleans about the storm.
Both Obama and McCain have sharply criticized Bush's response to Katrina and are eager to assure voters they would handle a natural disaster in the United States differently.
"Obviously this is a very serious situation," Obama said of Hurricane Gustav, adding he was monitoring events closely.
"The main priority had to be making sure that everything is being done on the ground to prevent a repeat of some of the tragic situations we saw several years ago."
McCain and his wife, Cindy, spent time getting to know Palin, her husband, Todd, and their children on Saturday, visiting voters at a diner in Pittsburgh and holding a rally in the town of Washington with a crowd estimated at some 10,000.
Palin, the first woman to be nominated as vice president on a Republican ticket, drew boos from an otherwise enthusiastic crowd when she referred to New York Sen. Hillary Clinton's failed bid for the Democratic nomination.
The Arizona senator announced his vice presidential choice on Friday after hosting Palin at his Arizona home on Thursday. It was only the second time the two had met in person.
Obama's running mate is Delaware Sen. Joe Biden.
Palin's conservative credentials, including strong anti-abortion views and a record of confronting entrenched interests during less than two years as governor of Alaska, energized conservatives, who poured money into the campaign.
The campaign raised nearly $7 million on Friday alone, its best single day of fundraising yet, officials said.
Obama, who would be the first black U.S. president, praised Palin but ducked questions on whether she was prepared for the job. "I think that Gov. Palin is a compelling person. She's got a great story," he told reporters.
"I think you guys can take a look at Gov. Palin's and Joe Biden's record and make your own judgments in terms of who you think has what it takes to be an outstanding vice president.
Seeking to highlight skepticism of McCain's pick, the Obama campaign sent out an e-mail with dozens of quotes from editorials across the country, including Palin's home state of Alaska, where she is popular, questioning her preparedness.
"Republicans rightfully have criticized the Democratic nominee, Sen. Barack Obama, for his lack of experience, but Palin is a neophyte in comparison," wrote Alaska's Fairbanks Daily News-Miner.
"Governor Palin's lack of experience, especially in national security and foreign affairs, raises immediate questions about how prepared she is to potentially succeed to the presidency," wrote The New York Times.
Frank Donatelli, deputy chairman of the Republican National Committee, dismissed the criticism.
"Senator McCain has not only succeeded in unifying our party, but also in generating great enthusiasm," he said.
Additional reporting by Caren Bohan, Tim Ryan and Jeremy Pelofsky