If Democrats retain all of their existing seats, they would end 12 years of Republican rule, rise to power and clear the way for Rep. Nancy Pelosi, D-Calif., to become the country's first female House speaker.
"We are on the brink of a great Democratic victory," Pelosi predicted.
The results would give Democrats power in the House for the first since 1994, when a rebellious GOP gained a majority.
"On issues like immigration, more Democrats agree with Bush than Republicans even. There's some consensus on other issues like healthcare and energy policy and maybe even tax reform," CBS News political consultant Norm Ornstein says.
"The challenge is that almost all moderate Republicans in the House and even some in the Senate are wiped out. If you move to the middle, there are some Republicans you'll have to convince to move with you. Bush will also have to work with Democratic leaders who don't like him and don't trust him. And the feeling is mutual," Ornstein says.
According to CBS News exit polls, voters said national issues outweighed local ones by roughly 2-to-1. Exit polls showed that nearly 60 percent of voters disapprove of the Iraq war. Most voters said their minds were made up at least a month ago.
Pelosi represents one of the most liberal districts in the nation and is notable for her sharp criticisms of the Bush administration.
"Pelosi will have a full-time job just keeping her caucus together. The Democrats are badly fractured on fundamental issues. The leadership is very much further to the left than the members," says CBS News Democratic political consultant Harrison Hickman.
The 15th and clinching seat win for Democrats came in Florida with Tim Mahoney's defeat of Republican Mark Foley, whose inappropriate e-mails with a House page doomed his re-election, CBS News estimates.
Scandal also played a role in Democrat Nick Lampson's capture of former Republican House Majority Leader Tom DeLay's seat in Texas. DeLay left Congress following his alleged involvement in the Jack Abramoff-lobbying scandal.
However, Republican Tom Reynolds of New York, a key figure in the page scandal, avoided defeat, beating out Democrat Jack Davis, CBS News estimates.
The first pickup of a Republican seat was in Indiana, where county sheriff Brad Ellsworth was the winner over GOP incumbent John Hostettler, a leading voice for social conservatives who was first elected in 1994, CBS News estimates. Also, Nancy Johnson, Connecticut's longest-serving House member, lost her re-election bid and five-term Congressman Jim Ryun, R-Kan., lost his seat.
Former NFL quarterback Heath Shuler, a Democrat, defeated Republican Charles Taylor in North Carolina.
Other projected Democratic wins were:
"You could make the case that this is an opportunity for Bush," says Ornstein. "The first reaction after Democrats were wiped out '94 was that it would be the end of the presidency for Clinton, but it ended up being a savior. Things got done. It gives Bush an opportunity to create a majority in the middle. Now, he has to take advantage of this opportunity, but Democrats have a strong incentive in getting legislative successes, especially because many won by small margins in Republican territories."
The remaining incumbent Republicans in Connecticut's Republican congressional delegation, Christopher Shays and Rob Simmons, were in tight races.
Shays declared victory at his Norwalk headquarters late Tuesday, even as he and Democratic challenger Diane Farrell appeared almost neck-and-neck in late returns.
"It was an amazing political race. We ran against a tidal wave
against Republicans. I believe that the people of this district
have re-elected me because of what I have done in 19 years," Shays
The GOP's fourth-highest ranking member of the House, Deborah Pryce of Ohio, narrowly kept her seat by a 51-49 margin, CBS News estimates.
Republicans spent months trying to beat back well-funded Democratic opponents in districts stretching from New Hampshire to California. In the campaign's homestretch, Democrats widened the battlefield by going after Republicans in states that historically have been solid GOP territory.
In addition to the Iraq war, Democrats capitalized on Republican scandals and the public's overall disenchantment with having the Presidency and Congress in the hands of the same party.
All 435 House seats were up for grabs Tuesday.
"We're seeing a huge turn in independent voters to the Democrats. National exit polls show a significant advantage for Democratic candidates," says CBS News political consultant Stu Rothenberg.