Handicapping the Senate landscape is an increasingly volatile exercise these days, with Democrats highly competitive in deeply conservative states while Republicans hold their own in the Northeast and other unfriendly confines (as I wrote in my column last week). This is not your wave environment of 2006, 2008, and 2010--it’s one where candidate strength matters a lot, even as the presidential race will be shaping the down-ballot landscape.

But even as the overall picture holds many possibilities, this week demonstrated how the seeds are in place for Democrats not only to hold the Senate but also to prevent any losses at all. That would be a remarkable turnaround for a party that looked resigned to losing seats, and a stinging setback for National Republican Senatorial Committee Chairman John Cornyn, who set 2012 as the year when Republicans would ascend back into power.

The formula, which looked near-impossible several months ago, now is quite realistic. It would mean that the Democratic fundamentals in Massachusetts, Connecticut, and Wisconsin would assert themselves and propel flawed nominees such as Elizabeth Warren, Rep. Chris Murphy, and Rep. Tammy Baldwin to victory. This past week signaled Democratic momentum in Massachusetts and Wisconsin, with several polls showing Warren moving ahead in Massachusetts, while developments about Tommy Thompson’s cash flow and campaign skills suggest that Democrats have an opportunity to make headway in Wisconsin.

The polls in Massachusetts show that, despite Warren’s underwhelming campaign, a presidential-year electorate in the deeply Democratic state could still be enough to push her ahead of Rerpublican Sen. Scott Brown. Four separate public polls, all released in the last week, show Warren running ahead of Brown by varying margins between 2 and 6 points. Adding insult to injury, Brown quickly distanced himself from Mitt Romney’s “47 percent” fundraiser comments, knowing that even a small political hit could mean the difference in the close race.

Story continues

Wisconsin is more favorable for Republicans, given Thompson’s high name identification and broad (if not deep) popularity from his decade-long stint as governor in the 1990s. But the same challenges that he faced in the Republican primary, when he barely inched out several underwhelming opponents, are reasserting themselves in the general election. Still distrusted by many movement conservatives, he’s had trouble raising money in the general election despite his big-name profile. His track record as a lobbyist is still poisonous in this anti-Washington, anti-incumbent environment. He has the good fortune of running against an opponent, Baldwin, who is well to the left of the Wisconsin electorate.

But she’s run the better campaign so far, downplaying her legislative record in favor of taking populist stands against China and touting her work across the aisle. Indeed, a new Marquette poll shows Baldwin leading Thompson, 50 percent to 41 percent, on the heels of a significant edge for President Obama on the presidential ticket in Wisconsin.

Thompson is still the favorite, and he has plenty of territory to mine against Baldwin. But if the Romney presidential ticket falls short in Wisconsin, Thompson is far from a sure thing.

That brings us to the pack of Republican-friendly states that are showing signs of life (or more) for Democratic candidates: Missouri, North Dakota, Montana, and Indiana. With clear signs that Rep. Todd Akin is sticking in the race in Missouri, Republicans view a seat they assumed that Democrats would lose as their own lost cause. (Even if it’s competitive, the pledges from outside groups to withhold money with Akin in the race make a loss a self-fulfilling prophecy.) North Dakota and Montana are more competitive than both parties expected. If the national environment asserts itself in those states, however, they still favor Republicans.

But the biggest game-changer over the past week has been Indiana, where Republicans are showing signs they’re concerned about the candidacy of Richard Mourdock. Mourdock, who was the conservative lion killer in defeating Richard Lugar in the GOP primary, has run an underwhelming general-election campaign against Democratic Rep. Joe Donnelly. Both campaign committees are investing significant money in Indiana, the surest sign the race is highly competitive. (Democratic polling also shows Donnelly with a narrow edge.)

In the 2010 electoral environment, even a flawed conservative candidate would have been able to win an open seat easily, as Republican Dan Coats dispatched up-and-coming Democrat Brad Ellsworth with ease. But 2012 is shaping up to be more evenly matched, with higher African-American turnout expected from the cities and Donnelly’s blue-collar appeal potentially winning over soft Republicans. Several GOP strategists tracking the race said it is no better than a toss-up for the party--a far cry from the solid position Mourdock assumed he was in post-primary.

Finally, the battle for the Senate will be decided by the battleground-state races, where the presidential ticket will play an outsized role in determining the fate of the down-ballot candidates: Virginia, Nevada, Ohio, and Florida. The presidential race in all four of those states is close, but Obama has gotten late post-convention momentum that’s boosting his prospects in all three. In Ohio and Florida, less-than-stellar Republican nominees Josh Mandel and Rep. Connie Mack desperately need Romney to win their states by a healthy margin to pull them across the finish line. That’s looking less likely by the day.

In Virginia, both former Sen. George Allen and Tim Kaine are as reliant on their presidential nominees as anyone in the country. If Obama wins the state, likely propelled by high minority and youth turnout, Kaine is in good shape. If Romney wins, though, it’s a very good sign for Allen’s prospects, and would be a signal that the enthusiasm gap asserted itself in favor of the GOP.

Sen. Dean Heller is the stronger candidate in Nevada, but if the Democrats’ turnout machine replicates itself in 2012, he could find himself in a closer-than-expected race with Rep. Shelley Berkley. If there’s one state that confounds the weak economic data, it’s Nevada, which looks primed to back Obama despite very high unemployment and a foreclosure crisis. That dynamic could boost Berkley, if she holds her own in the campaign.

So let’s go to the Senate scoreboard. If Republicans still manage to pick up seats in the deeply conservative states: Nebraska (a near lock), North Dakota (far from a lock), and Montana (another close race) but lose Maine, Massachusetts, and Wisconsin while fumbling away Indiana, we’re at the status quo. There are other paths to an even-steven Senate breakdown: If Republicans hang on to Indiana but a strong Democratic turnout in Nevada ousts Heller, same situation.

Republicans, meanwhile, need more of an inside straight. Hang on to the seats in Republican states (which alone account for three pickups), hold Massachusetts, and pick up Wisconsin and Virginia. That would give them four seats, enough for a bare 51-49 majority. An upset in Connecticut would allow for a little more wiggle room.

At the beginning of the year, it was hard to envision Democrats holding a Senate majority, given both the Republican-friendly landscape of states contested and the expectation that there would be many competitive races in battleground states. Not only have Democrats held their own in the solidly Republican states, but Republicans haven’t been able to threaten seemingly-vulnerable incumbents, like Sherrod Brown, Bill Nelson, Debbie Stabenow, and Bob Casey. (Shockingly, Sen. Jon Tester could reasonably be the only Democratic senator to fall.)

There’s enough uncertainty, and enough races still in play, that Republicans could still muster a net of four or five seats. But those prospects are looking dimmer by the day.