It's never too early to speculate, is it? Charlie Cook already has early ratings posted for the 2006 (and the two 2005) gubernatorial races, as well as the Senate races for that year.
Here's a quick rundown of what to expect...
GOVERNORS
First, New Jersey and Virginia both have races in 2005, and Cook lists both as tossups. I have to agree. In Virginia, you've got Mark Warner leaving office because of term limits, and what promises to be a hotly-contested race between Lt. Gov. Tim Kaine (D) and AG Jerry Kilgore (R). It's already getting heated, in fact. I think this is a good test of Democratic strength in Virginia; can Democrats establish a good base here, or was Mark Warner's 2001 victory a fluke?
In New Jersey, you've got a generally Democratic state, but the scandal surrounding former Governor Jim McGreevey could give Republicans a shot. Given Jon Corzine's ability to self-finance, I'd have to give a slight edge to him should he win the primary.
Among races in 2006, only one of the 14 Democratic state houses is considered a tossup (Iowa). There, you've got Governor Vilsack retiring after two terms, with plenty of action on both sides. It's hard to even think of who will be Iowa's next governor, since both primaries are relatively crowded and Iowa is a classic swing state.
Of the 22 Republicans up for reelection, seven are considered tossups -- and it really could be more. Four are open seats thanks to term limits -- Arkansas, Florida, Colorado, and Nevada. All happen to be swing states. In addition, there's Frank Murkowski in Alaska, with his host of problems. And there are two Governors in solid blue states -- Bob Ehrlich and George Pataki -- who have already drawn very strong Democratic challengers.
In general, though, the Democratic governors up in 2006 are safer. In fact, Cook lists 12 of the 14 governors as either Solid or Likely Democratic. The four Solids are Blagojevich, Richardson, Kulongoski, and Bredesen (yeah, Tennessee's a red state, but have you seen his approval ratings?) Only John Lynch of New Hampshire, elected in 2004, is placed in the Lean Dem category, and it's hard to see him making the kind of mistakes that caused New Hampshire voters not to give Craig Benson a second term.
In addition to the tossups on the Republican side, there are several governors in the Lean category who could have problems. Riley in Alabama and Perdue in Georgia have some fairly deep problems, although, it must be noted that Riley's main threat seems to be coming from Republicans and not Democrats. Mitt Romney and Don Carcieri are sitting in solid blue states, and perhaps the only reason neither is considered a tossup is because they haven't drawn the sort of high-profile challengers that Ehrlich and Pataki have. Tim Pawlenty in Minnesota is in a somewhat similar situation, though his state is much less Democratic. And then there's the open seat in Ohio -- why is this here? We need a solid challenger in Ohio.
The only other contests really worth noting are Texas (Likely R), where Rick Perry is in more trouble in the primary than in the general election; California (Solid R) -- apparently we have little shot at beating Arnold; and the open seats in Idaho and Nebraska, which are, well, Idaho and Nebraska.
SENATORS
Only one of the 18 Democrats up for reelection is considered a tossup, and that's Mark Dayton. Who is challenging Dayton?
The two Nelsons, Cantwell, Stabenow, and Corzine are listed as Lean D. Ben Nelson dodged a bullet since neither Mike Johanns nor Tom Osborne will challenge him, but given Nebraska's politics, a second-tier Republican could still give him a tough race. With Corzine, the bigger concern is that the seat will be open if he's elected governor. If Corzine runs for reelection, he should win rather easily. As for retirements -- none that I can see would make much difference, except perhaps for Robert Byrd, but who can Republicans run in West Virginia?
The Republicans have three tossups -- Santorum, Chafee, and Frist's seat. Santorum, of course, is too far to the right for PA, but that hasn't stopped him from winning two Senate elections, so perhaps he shouldn't be underestimated. And given the threats by Club for Growth, Chafee might as well seal his reelection by running as a Democrat. Of course... if he did that, some ambitious Democrat might still challenge him in the primary.
Talent, DeWine, and Allen are listed as Likely... don't know what puts Talent and Allen here rather than Lean, except perhaps for a lack of challengers. (Mark Warner, for all the speculation, is not considered a candidate for the Senate as of right now.) Potential retirements in the Solid R category include Lugar, Hutchison (could run for Gov.), Hatch, and Thomas, though none is in particularly friendly territory for a Dem.