Texas Gov. George W. Bush today will shatter the presidential fund-raising record set by the money machine that fueled the 1996 Clinton-Gore reelection, reporting more than $23 million raised in the first half of this year, according to GOP sources, and far outpacing all other White House hopefuls including Vice President Gore.

At the same time, Gore is facing an unexpectedly strong challenge for Democratic dollars from former New Jersey senator Bill Bradley. Gore's campaign said yesterday he has collected between $18.2 million and $18.5 million this year, while Bradley campaign sources said he has raised more than $11 million.

Gore's effort puts him below what party sources said was the $20 million they had hoped to collect and fund-raising veterans in both parties said they were impressed by the Bradley showing, which has been boosted by a network of sports celebrities supporting the former New York Knick and has relied heavily on Bradley's appeal to Wall Street executives.

Today marks the official end of a key "financial primary" in the early-starting 2000 presidential contest, and with last-minute contributions still flooding in to the campaigns by the June 30 deadline, the numbers they disclosed yesterday were still estimates.

Republican sources said in particular that Bush's already formidable bank account was likely to be significantly larger by the end of today, with the candidate still in the midst of a three-day California tour expected to raise more than $4 million.

In 1995, the Clinton-Gore team raised just under $20 million in the first six months, $9.9 million of that in the second quarter -- at the time, a record-setting early effort. But Bush, who started his fund-raising operation only in March and did not hit the road in search of campaign cash until earlier this month, has translated the cachet of his name and strong early poll standing into overwhelming support among the GOP's donor base. Bush raised $7.6 million in the first quarter, so his second-quarter total will be well over $15 million.

"We have a network of over 2,000 volunteers and they're rushing to get their money in by the deadline," a Bush campaign official said yesterday. The record-breaking quarter, the official said, "represents support. It's important because it shows the breadth of support."

Bush's success at mobilizing a network of "Pioneers" dedicated to collecting $100,000 or more for his campaign and a series of huge fund-raisers this month have given him an insurmountable cash advantage over the rest of the crowded Republican field.

Elizabeth Dole, after raising just $700,000 in the first quarter of this year, will win the race for Republican second place this time with $2.7 million raised this quarter, just ahead of millionaire publisher Steve Forbes and Arizona Sen. John McCain, who each collected about $2.5 million this quarter.

"Obviously, Governor Bush is in a league by himself," said Dole spokesman Ari Fleischer. "She beat all the rest."

But McCain, whose chairmanship of the powerful Senate Commerce Committee has enabled him to raise money from key industries under the panel's jurisdiction, is in second place to Bush as far as overall fund-raising this year. All told, he has collected $6.1 million for his White House campaign, including a $2 million transfer from his Senate campaign account.

It's among the rest of the GOP field that the Bush fund-raising may have its most immediate impact. Former vice president Dan Quayle, for example, has raised about $3.4 million this year, but only $1 million of that this quarter, his campaign said. Ohio Rep. John R. Kasich has taken in only about $600,000 this quarter. And Lamar Alexander, the former Tennessee governor who recently laid off several key aides to conserve money, has raised about $1.5 million this quarter.

"Someone is going to emerge as the alternative to Governor Bush, but if you don't have the money to get yourself through the long summer, you might not be around when the voters get around to choosing their alternative," said a Kasich aide, who nonetheless insisted that his candidate's $1.7 million cash on hand was enough for him to remain a viable alternative.

On the Democratic side, the rivalry between Gore and Bradley has turned into more of a competition for dollars than the vice president's large lead in the polls and strong backing by the party establishment would have suggested. For the second quarter, Gore will have raised about $9 million to Bradley's approximately $7 million.

"The margin we're most interested in is the margin we're widening among Democratic voters," said Marla Romash, deputy chairman of the Gore campaign, referring to recent polls that show him with a strong lead over Bradley.

Romash also dismissed Bush's ability to outraise the sitting vice president, saying, "Republicans always have more money than Democrats."

A Democratic lobbyist warned it would be a mistake for Gore to get into a money competition with Bush. "You get in a fund-raising race with a Republican and you get beat every time," he said.

But in recent days, the Gore campaign has been aggressively leaning on fund-raisers to meet or exceed their second-quarter targets, the lobbyist said. Gore himself has been busily raising money right up until today's deadline: He was in Pennsylvania on Monday for two fund-raisers, visited Florida yesterday and will hit New York City today.

Staff writer Ceci Connolly and staff researcher Ben White contributed to this report.