With President Bush's ratings at rock-bottom, fewer Republicans signing up to vote, and voters nationally gravitating toward Democrats in public polls, the GOP is bracing for defeats in November that will expand Democrats' now razor-thin 51-49 majority in the Senate.
Democrats have solid chances of winning five seats, according to strategists in both parties and public polls, and realistic shots at picking off another three to five Republican senators. Republicans have only one good opportunity for replacing a Democrat, in Louisiana.
A quirk of the political calendar - Republicans are defending 23 seats this year to Democrats' 12 - put the GOP at a disadvantage from the start. Worse still, those include five Republican retirements - which typically make it harder to keep a seat - compared to none among Democrats.
The scent of defeat threatens to become a self-fulfilling prophecy: Republican donors are sitting on their hands, giving Democrats a nearly 2-to-1 advantage in fundraising that limits the GOP's ability to defend key seats.
Democrats are pouring cash into TV advertising and on-the-ground voter mobilization. They're competing aggressively in 11 states, including GOP strongholds like Alaska, North Carolina and Virginia that they hope to convert by translatingappeal to African American and young voters into wins for Democratic Senate candidates.
"It shapes up to be a very good Democratic year. This could be one of those change elections - I call them tectonic," said Sen. Charles E. Schumer, D-N.Y., the head of his party's Senate campaign arm, which has $46.2 million in the bank.
Sen. John Ensign, R-Nev., the GOP Senate campaign chief, says he'll be lucky if his party can hold its losses to two seats - a more optimistic assessment than just a few weeks ago, when he said the best case scenario would be four losses.
"I'm getting a little bit more optimistic," said Ensign. "There's no question the challenges have been huge."
His top goal now is meeting a low bar - retaining sufficient numbers to deny Democrats the 60 votes they would need to break filibusters. Today, the GOP Senate campaign arm has $24.6 million and has yet to run an ad.
Most strategists see a 9-seat gain for Democrats as next to impossible. Schumer said there would have to be "a huge hurricane." To get there, everything would have to go Democrats' way.
They would have to sweep competitive contests in Alaska, Colorado, Mississippi, New Hampshire and Oregon while closing the deal in two states they are now favored to win: New Mexico and Virginia. Both those races are open with the retirements of longtime GOP Sens. Pete Domenici in New Mexico and John Warner in Virginia.
Then Democrats would have to beat at least two more Republican incumbents in tougher challenges to Sens. Susan Collins in Maine, Norm Coleman in Minnesota and Elizabeth Dole in North Carolina. Emboldened by money and the poor climate for Republicans, they're also eyeing even longer-odds GOP bastions like Georgia and Kentucky, home to Minority Leader Mitch McConnell.
The only real challenge for a seat now held by a Democrat is in Louisiana, where Sen. Mary L. Landrieu has never drawn more than 52 percent of the vote and is up against Republican State Treasurer John Kennedy. Strategists in both parties have long expected that race to be close.
They also agree that Democrats are very likely to win seats to replace retiring Republicans in New Mexico - where Democratic Rep. Tom Udall is running well ahead of GOP Rep. Steve Pearce - and in Virginia - where former Gov. Mark Warner is favored to beat former Gov. Jim Gilmore.
Democrats are also running strong in a handful of states that previously seemed out of reach.
In Alaska, their quest to defeat Sen. Ted Stevens, the longest-serving GOP senator, got a boost with his recent indictment on felony charges of hiding a quarter-million dollars' worth of gifts from an oil company. Democrats have groomed Anchorage Mayor Mark Begich, who's well-known in the state because his late father was a legislator and congressman, to challenge Stevens.
If Stevens wins his six-way primary Aug. 26, the outcome of the November race could turn in large part on the verdict in his case, which goes to trial less than six weeks before Election Day.
In Colorado, public polls show Democratic Rep. Mark Udall in a dead heat in his race against former Republican Rep. Bob Schaffer to succeed retiring GOP Sen. Wayne Allard. Schaffer has been dogged by accusations he was tied to convicted lobbyist Jack Abramoff, but has gained traction recently by attacking Udall for his opposition to more oil drilling at a time of rising gas prices.
Another tight race is in New Hampshire, where incumbent Republican Sen. John E. Sununu is in a rematch against former Democratic Gov. Jeanne Shaheen. The state is famously independent and unpredictable, but it's turned more Democratic since Sununu eked out a 4-point win over Shaheen in 2002, and the sour public mood toward Republicans is helping Shaheen.
A tough environment for Republicans also has put Oregon into play. Democrat Jeff Merkley, the statehouse speaker, is challenging Sen. Gordon Smith, a two-term moderate Republican so eager to distance himself from his party that he ran an ad boasting of his ties to Obama. National Democrats are countering with ads of their own that call Smith a friend of Big Oil.
Democrats are also advertising in strongly Republican Mississippi, where they hope Obama will spark turnout among African-American voters high enough to help knock out Sen. Roger Wicker. Wicker faces former Gov. Ronnie Musgrove in a special election to serve out the remaining four years of retired Sen. Trent Lott's term.
A similar dynamic could play out in North Carolina, where the potential for high black voter turnout is causing unexpected worries for Dole. For now, she leads Democratic state Sen. Kay Hagan in both polls and fundraising in North Carolina's first-ever all-woman Senate contest.
Democrats have uphill battles in a couple of states where they had hoped to be well ahead of Republicans.
In Minnesota, Coleman is holding his own in a race against comedian-turned-candidate Al Franken, who has been battered with criticism for a satirical column he wrote for Playboy Magazine in 2000 called "Porn-O-Rama!" and for tax-filing irregularities.
And in Maine, Collins is relying on her reputation for reaching across party lines to counter Democratic Rep. Tom Allen's attempts to tie her to Mr. Bush.
Reaching even further to into Republicans' comfort zone, Democrats also hold out hopes - if everything goes their way - of ousting McConnell, a master of Senate rules who has been a constant thorn in their side, or Sen. Saxby Chambliss in Georgia.