In a bid to rake in big money for the Arizona senator and Republican congressional candidates, Bush will be in the Rocky Mountain states, New Mexico, Arizona, Utah and Kansas, the White House said. The events are closed to the media.
"The reason that they're closed is that the McCain campaign has a practice of having their fundraisers as closed press," said White House spokeswoman Dana Perino.
Bush and McCain will appear at one fundraiser together, she said, adding that the two might appear in public together.
"Stay tuned for the details, but I think that you'll see a -- when we arrive or when we depart, I think there will be a chance," Perino said.
"President Bush is a formidable campaign fundraiser, as has been reported over the years, and I expect that he'll continue to be," Perino told reporters.
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