Republicans face stiff odds in their bid to reclaim a Senate majority, but Democrats have even a tougher climb to take back the House, a final, state-by-state rundown of Tuesday's midterm election prospects shows.

The canvass of insiders in both parties and of neutral observers by Washington Post reporters concludes that the GOP would have to win three of four tossup races -- if all 30 other Senate contests followed form -- to emerge with 50 seats and allow Vice President Cheney's tie-breaking vote to prevail.

On the other side of the Capitol, Democrats need a net gain of six seats to capture control. They would have to sweep all the tossup House races and eight of the 24 now rated as leaning -- but not certain for Republicans -- to reach that target. If all favored candidates won and the contests rated too close to call split evenly, the GOP would actually add three seats to its House majority.

Inevitably, there will be surprises in the hard-fought congressional campaigns -- a favorite who falls -- but the most likely shift of political power will take place in the governorships. There, Democrats are poised to make significant gains, including takeovers of such major electoral prizes as Pennsylvania, Michigan and Illinois.

Unlike such past years as 1982 and 1994, when midterm elections produced sizable shifts in the party balance, polling and reporting failed to discern any broad national trend that would let the country break out of the nearly perfect 50-50 split demonstrated in the 2000 election results.

Matthew Dowd, a Republican National Committee strategist, said, "It's all campaign- and candidate-specific. There's no global move in either direction. It's going to come down to the enthusiasm of each party's base to decide so many of these races."

House Minority Leader Richard A. Gephardt (D-Mo.) disagreed, saying, "I have felt for some time things were moving in our direction, primarily because of the economy and the whole cluster of . . . retirement security issues."

But the race-by-race reporting found almost as many instances of Republicans closing with a rush against Democrats -- particularly in places where President Bush touched down in his final frantic week of campaigning.

"No question he moves the numbers when he lands," one Democrat said. "He's the best tool the Republicans have. It takes us thousands of phone calls and door-to-door visits to stir up our base the way he can stir up theirs."

Yet it appears likely that Bush will have to settle for the same half-a-loaf result as Democratic leaders.

Ken Mehlman, the White House political director, said, "If Republicans are able to keep control of the House, President Bush will have had the best off-year election in 40 years. If Republicans are able to win back the Senate, it will have been an even more historic day."

The first seems much more likely than the second. Counting carryovers who do not face the voters until 2004 or 2006 and safe seats up this year, Republicans have 44 assured Senate votes and Democrats 45, not counting Independent Sen. James M. Jeffords of Vermont, who will support the Democrats on organization matters.

Each party has three races that are leaning its way, but are not certain. For the Republicans, those states are Missouri, North Carolina and Texas; for the Democrats, Arkansas, Georgia and Minnesota. Missouri appears the likeliest seat to fall to the Republicans, while Arkansas represents the Democrats' best opportunity to gain a seat -- offsetting one another.

If those followed form, Republicans would have 47 seats, Democrats 48, again not counting Jeffords.

The true tossup races are in Colorado, New Hampshire and South Dakota, but Louisiana must be added to the list because it is uncertain whether Sen. Mary Landrieu (D), who leads the field in an all-party primary including three Republicans, will receive 50 percent of the votes as the state constitution requires. If not, she will face a runoff with a Republican on Dec. 7, in which her chances might not be as good. Republicans would need victories in three of those four states to reach the magic number of 50.

A business-oriented political operative, who maintains close contact with Republican campaigns, said, "My own guess is that Republicans will wind up closer to 46 than to 50."

On the other hand, a senior labor politico conversant with Democratic operations said, "The House is not in play for us. I'm more worried about the Democrats holding where they are."

The Post's reporting bears out his view. Republicans can count 201 safe or likely seats, and the grass-roots reports identified 24 more hotly contested races where Republicans seem to be ahead, bringing them to 225 -- seven more than a majority.

The comparable figures for the Democrats are 190 safe or likely seats and 13 battleground districts where they may be ahead, a total of 203. Democrats would have to win all seven of the tossup races and defeat eight of the 24 favored Republicans to oust Rep. J. Dennis Hastert (R-Ill.) from the Speaker's chair and take back control of the House agenda, which they lost in the GOP landslide of 1994.

The two parties have poured millions of dollars into the most competitive districts to supplement the bank accounts of the candidates, but down the stretch the Republicans have had a clear edge in money, and it appears to have paid off in moving candidates from the endangered list to the probable winners list.

Although the party that holds the White House normally loses seats in the first midterm election of a new presidency, the Democrats also are bucking history this year. After losing the House in 1994, Democrats picked up seats in 1996, 1998 and 2000. But no party has gained seats in four consecutive House elections since the Republicans did it early in the last century.

Bush's solid approval ratings, boosted by his handling of the war on terrorism after the attacks of Sept. 11, 2001, have given Republicans something unexpected in midterm elections: the absence of a drag on their candidacies. That has given GOP candidates the opportunity to fight for survival on their own, and has made the Democrats' task more difficult.

The biggest change in power will come among the nation's governors, where term limits and retirements alone will mean 20 new faces within the gubernatorial ranks. The weak economy and a sharp drop in tax receipts have devastated state budgets, creating more volatility in the governors' races than in contests for House or Senate.

Democrats appear set to regain the majority of governorships for the first time since surrendering that advantage to the GOP in the 1994 elections. With 11 governors' races rated in the tossup category, however, that could be a bare or a more significant majority by the time all races are decided.

The most significant Democratic gains will come in the big industrial states that took Al Gore to the brink of the presidency two years ago but where the governorships have been in GOP hands for a decade or more. Democrats expect to pick up governorships in Pennsylvania, Michigan, and the likely winners -- former Philadelphia mayor Edward Rendell and Michigan attorney general Jennifer Granholm -- will quickly become national players.

Democrats have a clear edge in Illinois, where scandals in the administration of retiring Gov. George Ryan (R) make the Democrats' time-for-a-change argument potent. Democrats have a much narrower edge in Wisconsin against Gov. Scott McCallum (R). In Iowa, a strong Republican campaign may fall short of unseating Gov. Tom Vilsack (D). Republicans may pick up the governorship in Minnesota, where Gov. Jesse Ventura (I) decided to retire rather than face a difficult reelection campaign, but the race is close.

Meanwhile, Republicans are fighting to strengthen their southern flank after losing a series of southern governorships the past four years. Alabama Gov. Don Siegelman (D) and South Carolina Gov. Jim Hodges (D) are the most endangered incumbents in the region in their reelection bids. Democrats could pick up Tennessee.

In the most closely watched governor's race in the nation, Florida Gov. Jeb Bush (R) appears likely to hold off the challenge from Democrat Bill McBride. But the state is the scene of a frenzy of political activity this weekend, with visits by Bush, former president Bill Clinton and former vice president Al Gore. Election Day there will see one of the most intensive get-out-the-vote battles in the country.

Republicans are seeking to solidify their strength in the Northeast. Incumbent Govs. George E. Pataki (R) of New York and John Rowland (R) of Connecticut are coasting toward third terms, and New Hampshire is likely to flip to the GOP. Republicans are in far tougher fights, however, to hold governorships in Massachusetts and Rhode Island.

Democrats have nine female candidates for governor. The likeliest winner in addition to Michigan's Granholm is Kansas insurance commissioner Kathleen Sebelius. But female Democratic candidates also are running even or narrowly behind in Arizona, Massachusetts, Rhode Island, Hawaii (where the Republican candidate also is a woman), Alaska and Arkansas. In Maryland, Lt. Gov. Kathleen Kennedy Townsend (D) remains in an unexpectedly difficult race against Rep. Robert L. Ehrlich Jr. (R).

Democrats should gain seats in Maine and New Mexico, while Republicans could win in Oregon. The Vermont legislature may pick the winner there if no one gets 50 percent of the vote, as seems likely.

The luckiest incumbent in the country is California Gov. Gray Davis (D), who is so unpopular after his first term that he has struggled to get above 42 percent in many public polls. Had he drawn a more credible opponent, he might be on his way to retirement Tuesday, but the campaign of challenger Bill Simon (R) has been so mistake-plagued that Davis likely will win a second term.

Staff writer Juliet Eilperin and political researcher Brian Faler contributed to this report.

Pennsylvania Democratic gubernatorial candidate Edward Rendell, right, appears to be the likely winner. North Carolina Republican Elizabeth Dole, left, thanks Noreen Foster for helping with Dole's Senate campaign.