While Sen. John McCain (R-Ariz.) hangs in there, locked in a tough race with Sen. Barack Obama (D-Ill.), the Republican undercard is facing obliteration in the 2008 general elections for the Senate. Polling suggests that a massacre may be in the offing — and one that’s possibly even greater than the worst of previous GOP years: 1958, 1964, 1974, 1986 and 2006.

Scott Rasmussen, whose site, www.rasmussenreports.com , follows these races closely, is producing truly hair-raising polling data.

Of the open Republican Senate seats in contention, Democratic victory seems very likely in Virginia (Democratic former Gov. Mark Warner now has 55 percent, while fellow former Republican Gov. Jim Gilmore stands at 37) and New Mexico (where Democratic Rep. Tom Udall takes 53 percent to GOP Rep. Steve Pearce’s 37 and 57 percent to Republican Rep. Heather Wilson’s 36). In Colorado, Democratic Rep. Mark Udall has a narrow lead over Republican Bob Schaffer (45-42). Nebraska would seem safely Republican, but a humongous black turnout in Mississippi could elect former Democratic Gov. Ronnie Musgrove, just as it led to a Democratic congressional victory in a bi-election this month. Score them: two Democrat, one leaning Democrat, one leaning Republican, and one Republican. A net loss of two or three seats.

And then there are the endangered incumbents. Three GOP senators are actually behind their Democratic challengers. Alaska’s Ted Stevens is behind Mark Begich by 47-45. Elizabeth Dole trails Kay Hagan in North Carolina by 48-47. And Jeanne Shaheen is well ahead of John Sununu in New Hampshire, 51-43. Stevens’s legal problems and the likely huge black turnout in North Carolina make all three states lean Democratic at this point.

Even when GOP incumbents lead, they are perilously under 50 percent. In Oregon, as of this writing, Gordon Smith leads Jeff Merkley by only 45-42 and Steve Novick by 47-41. And in Texas, John Cornyn leads Rick Noriega by only 47-43. In addition, Norm Coleman in Minnesota is hanging on by his teeth against Al Franken, 50-43; Susan Collins is only narrowly ahead of Rep. Tom Allen in Maine, 52-42; and in Kansas, Pat Roberts holds only a 52-40 lead over Jim Slattery. Mitch McConnell in Kentucky may also be in trouble.

So, among incumbents, score it three leaning Democratic, two tossups, and three leaning Republican.

Overall, that’s a likely Democratic pickup of five seats, with an eight-seat gain possible, and, in a partisan wipeout, a 12-seat shift.

Mon dieu!

In all likelihood, the filibuster will still remain a theoretical Republican option, but, in practical terms, may be beyond reach, especially if Obama wins the White House.

Driving the GOP’s imperiled Senate situation, or course, is a massive shift in party identification. While the two parties are normally about tied in party ID, the Democrats now enjoy a 44-30 advantage in the latest Fox News poll of April 29.A combination of the Iraq war, gas prices, the credit crisis and a looming recession are dragging down the Republican Party, big time.

So is a president with a 28 percent approval rating. Bush needs to go out and tell America that things are bad, but not that bad. There are solid signs that the economy may not be tanking after all. Unemployment, while rising, is still at historic lows. The credit crisis has not led to a wholesale collapse of the financial industry and the instability appears to be easing. And, in Iraq, we are approaching a more stable situation with lower combat deaths. Bush, who has largely been hunkered down in the White House, needs to hit the trail and move his ratings up into the mid- or high 30s, not an insurmountable challenge.

Will the endangered Republicans recover? Most have prevailed, in the past, by lifting their personal ratings out of possible danger early in the race. But when long-term incumbents find themselves mired in the high 40s or low 50s in vote share, it indicates a massive voter desire for change that is not likely to abate.

In the House, the incredible three Democratic bi-election victories, combined with the retirements of so many Republican incumbents, indicates that the GOP may be facing disaster there as well.

This is not a good year to be a Republican.

Morris, a former adviser to Sen. Trent Lott (R-Miss.) and President Bill Clinton, is the author of Outrage. To get all of Dick Morris’s and Eileen McGann’s columns for free by email, go to www.dickmorris.com .