WASHINGTON — Democrats are positioned to make big gains in the House in next week's elections, adding 20 or more seats to their majority.

Republican candidates face a toxic mix of antipathy for President Bush, a sour economy, a huge financial disadvantage and a formidable Democratic campaign organization powered by presidential nominee Barack Obama. Few in their ranks feel safe, and a rush of GOP retirements is further feeding what is emerging as a Democratic wave.

With Obama leading Republican rival John McCain in key battleground states, the House GOP is in crisis-control mode.

"We have an uphill fight. We haven't caught very many breaks," said Rep. Tom Cole, R-Okla., the head of the Republican House campaign committee. "This is about getting the army across the river to the high ground on the other side."

Cole said the fate of Republican candidates is tied closely to McCain's, for good or ill. And while the campaign committee chief said McCain's bid had picked up momentum in its last days, he acknowledged it would take an improbable turnabout for the Republican to capture the White House and help limit GOP losses in Congress.

"We're hoping for a McCain upset, and certainly hoping we benefit from that," Cole said.

Still, strategists in both parties predicted privately that Democrats would pick up anywhere from 20 to more than 35 seats — the first time in more than 50 years that a party rode waves to bigger congressional margins two elections in a row. Democrats won 30 seats and control of the House in 2006, leaving them with a 235-199 majority, with one vacancy.

All 435 seats are up for grabs.

"Things are looking very good" for Democrats, said Rep. Chris Van Hollen, D-Md., the head of the party campaign committee. "We are going to break the historical curse and pick up a significant number of seats."

He declined to predict how large a majority Democrats would win but said there were at least 15 to 20 Republican seats that were dead-even races that could go either way.

That's a less pessimistic scenario for Republicans than even some top GOP officials sketch out. They are bracing for the loss of at least 15 seats and view more than 20 others as in serious jeopardy. They spoke on condition of anonymity to avoid publicly writing off Republican candidates in the crucial last days of the race.

The GOP lawmakers seen as most in danger of losing their seats include Alaska's Rep. Don Young, Rep. Marilyn Musgrave of Colorado, Rep. Tom Feeney of Florida, Rep. Robin Hayes of North Carolina and Michigan Reps. Tim Walberg and Joe Knollenberg.