* Laura Bush, Cindy McCain urge flood relief
* Thousands protest against Iraq war
* McCain expected at convention later in the week
By John Whitesides, Political Correspondent
ST. PAUL, Sept 1 (Reuters) - Republicans opened their convention on Monday in a somber mood, with Hurricane Gustav’s assault and Sarah Palin’s announcement of the pregnancy of her unmarried teenage daughter overshadowing John McCain’s show.
Palin, McCain’s newly announced running mate, said in a statement with her husband, Todd, that her unmarried daughter Bristol, 17, was pregnant and planned to deliver the baby and marry the father.
"We’re proud of Bristol’s decision to have her baby and even prouder to become grandparents," the Palins said in the statement. "As Bristol faces the responsibilities of adulthood, she knows she has our unconditional love and support."
The McCain campaign said it released the statement to counter Internet rumors that the Alaska governor’s five-month-old son was actually her daughter’s baby.
The announcement overshadowed a shortened opening session of the convention, as Republicans shifted from politics to storm relief while Gustav slammed into the Gulf Coast.
First lady Laura Bush and John McCain’s wife Cindy urged Americans to help Gulf Coast victims of the hurricane and said it was time to put aside politics.
"Our first priority now, today, is to ensure the safety and the well-being of those living in the Gulf Coast region," Laura Bush told the convention, which will nominate John McCain as its presidential candidate on Thursday.
"When such events occur we’re reminded that first we are all Americans and our shared American ideals will always transcend political partisanship," she said.
Fearing televised images of Republican festivities would be inappropriate as the storm slammed the Gulf Coast, McCain and his party limited the session to formal convention business and appeals for hurricane aid.
"Together we can accomplish so much to help those who have been affected," Cindy McCain said, joining Laura Bush on stage.
John McCain, 72, visited a disaster relief drop-off center in Waterville, Ohio, helping to pack cleaning materials, sponges, rubber gloves and other items into buckets labeled "Hurricane Gustav Relief Supplies."
"Thanks for your hard work," the Arizona senator said to volunteers packing the buckets on long tables.
McCain hoped to avoid comparisons to President George W. Bush, who was seen as out of touch for his failure to respond promptly to the devastation of New Orleans and the Gulf Coast by Hurricane Katrina three years ago.
As many as 10,000 protesters marched to the convention hall, chanting anti-war slogans and holding signs criticizing Bush. Police used pepper spray and smoke bombs against a few hundred violent protesters who broke away from the march.
The four-day Republican convention will nominate McCain and his vice presidential running mate, Alaska Gov. Sarah Palin, to face Democratic rival Barack Obama and his No. 2, Delaware Sen. Joe Biden, in the Nov. 4 presidential election.
A McCain campaign official said he raised $47 million in August, his biggest month yet, including $10 million he brought in since naming Palin as his running mate.
The Republican convention opens four days after Obama concluded the Democratic convention with an acceptance speech before 75,000 flag-waving supporters in a Denver football stadium.
Obama, 47, appeared at a labor rally in Detroit on Monday and asked for a moment of silence for those on the Gulf Coast. He canceled a planned trip to campaign in Wisconsin and returned to Chicago to monitor the storm.
"Today’s not a day for political speeches," Obama told supporters in Detroit.
Republican officials have not announced the convention schedule for the remainder of the week. McCain’s campaign manager Rick Davis told reporters he still expected McCain to deliver his acceptance speech in St. Paul.
Bush and Vice President Dick Cheney had canceled their appearances at the convention even before the schedule was reduced. The White House said Bush might address the convention later in the week.
Laura Bush and Cindy McCain urged convention-goers to help the Gulf Coast relief effort, and Laura Bush introduced videos from several Gulf Coast governors promising a strong response and urging support for the victims.
Both camps struggled with the political implications of the storm, trying to respond without appearing to be opportunists. Most opinion polls show Obama and McCain in a close race.
A CBS News poll showed Obama leading McCain by 48 percent to 40 percent in polling done Friday through Sunday, after the Democratic convention and the selection of Palin. Obama led by three points before his convention.
A USA Today poll taken after the Democratic convention showed a 7-point Obama advantage, up from four points before the gathering.
The conventions are a prime opportunity for candidates to make their cases for election to a general public that is just beginning to tune in, and the loss of one or more days could be a blow to McCain.
But some Republicans hoped McCain could benefit by demonstrating a strong and compassionate response to Gustav, further separating himself from Bush and his legacy.
(Additional reporting by Andy Sullivan, Steve Holland and Jeff Mason; Editing by Howard Goller and Jackie Frank)