So, McCain doesn’t have to worry about his money troubles because of Bush’s ability to raise large sums of cash. Even a president who is as unpopular as Bush can still rake in the cash:

The Democratic National Committee ended 2007 nearly flat broke, with cash of $2.9 million and debts of $2.2 million. Since then it has raised some money, paid down debt and managed to put $3.7 million in its piggy bank. This compares, however, with $25 million that the Republican National Committee has in cash on hand, after having raised $97 million since the beginning of 2007.
And with Senator John McCain now the presumptive Republican nominee, party officials started plotting with his campaign this week on deploying those resources against the well-financed Democratic candidacies of Senators Hillary Rodham Clinton and Barack Obama.
Already, President Bush, who spoke at 29 Republican fund-raisers and is credited with raising $63.5 million last year, is lined up for more R.N.C. fund-raising in the weeks ahead. This money is likely to provide the financial muscle for Mr. McCain to continue his attacks on both Democratic candidates.
[…]
“We’ve been preparing for the last several months,” Mr. Duncan said Wednesday. “We’ve been raising the money. We’ve been doing the research that’s necessary. We’ve been writing the victory plans that have been necessary to win the electoral votes. We’ve been putting the staff together. And all of that is available to Senator McCain, as our presumptive nominee, as of today.”

Ironic, isn’t it, that Bush should be the one who bills out McCain.
Now McCain doesn’t have to wait until September to spend money the RNC can do if for him.