Record spending to power 2008 White House race

"We recognize there is a fund-raising primary and so do our supporters," said Romney spokesman Kevin Madden, adding the money raised would not only fund the campaign but also offer a tangible sign of Romney's viability.

"It sends a big message about how serious we are," he said. "If we can do the fund-raising side of things, we'll show we can also perfect the field operations and grass-roots operations that are required for victory."

While the high cost of U.S. political campaigns has long sparked criticism, various proposals to reinvigorate public campaign financing have languished in Congress.

Like Bush and Kerry in 2004, top contenders in the 2008 primaries are expected to opt out of the public financing system and the accompanying spending caps. For the first time, the nominees also might opt out of the system in the general election, ensuring a high-dollar race from beginning to end.

Critics say the high campaign price tag reduces the influence of small donors and weeds out grass-roots candidates who rely on contributions of less than $200.

Running for president takes "ungodly" amounts of money, said Gary Kalman, an advocate with the U.S. Public Interest Research Group. "You winnow out the field too early before people have a chance to see who they like and hear their message," he said.

But long-shot candidates say a strong performance in early contests in Iowa or New Hampshire, where grass roots campaigning can trump a big wallet, can generate momentum and pump up their fund raising.

Former Gov. Tom Vilsack of Iowa, the first Democrat to jump in the race but an unknown quantity nationally, said he can be viable without matching the more well-known contenders dollar for dollar.

"It's not about having more money, it's about having enough money to compete," Vilsack said in an interview. "Will I outraise Hillary Clinton? Heck no, but I'll stack my ideas up against anybody's."