Going strictly on statistical history, 2010 should be a comeback year for Congressional Republicans.  Almost invariably, a new president's party loses seats in Congress in the first midterm following his presidential election.  In fact, tracking back over the last six presidents, five of them (Ford in '74, Carter in '78, Reagan in '82, George H.W. Bush in '90, and Clinton in '94) lost seats in the Senate in their first midtem.  The only president to gain seats was George W. Bush, whose party in 2002 was helped along by the the atmosphere emanating from the War on Terror and the September 11th attacks.

2010 will be Barack Obama's turn in the saddle, and for now, he looks more likely to be the exception to the rule, albeit not by much.  As it stands, Republicans will be defending as many seats as Democrats for (18 each) after defending more in each of the last two elections.  Four of those seats, however, will be contested in special elections: President Obama's Illinois seat, Vice President Biden's Delaware seat, Secretary Clinton's New York seat, and Secreatary Salazar's Colorado seat.  Democrats are poised to retain just about every seat they currently have, and have a realistic opportunity to pick up a few more.

But in all likelihood, this isn't going to be anything like 2006 or 2008, between the two of which Democrats went from a 5-seat minority disadvantage to a 10-seat majority advantage.  What's more probable is that if Democrats gain at all, it will be somewhere between two and four seats.

In laying out the potential outcomes, it helps to think of the races in tiers of competitiveness.  At the top, we have four key races that are likely to be tossups for the next few months, followed by six races that lean one way or the other (Caveat: any of this can change with a scandal or some big, unexpected news).

Connecticut - Tossup

Chris Dodd has taken a beating in the press for the apparently better-than-average mortgage he got on his house while pushing banking legislation, not to mention during a mortgage crisis.  There's a chance he could rebound, but in the meantime, he's polling just about neck and neck with Republican challenger Rob Simmons.  That's not a good sign for Dodd this early on, but ultimately could change in his favor.

Kentucy - Tossup

Democrats normally wouldn't have a shot in Kentucky, but Republican Jim Bunning seems intent on giving it to them.  Simply because the deeply unpopular Bunning is insisting on hanging around for a primary slugfest, Democrats have a real shot at the race.  If Bunning makes it through the primary, whichever Democrat wins his party's nomination has an excellent shot at taking the seat.

New Hampshire - Tossup

When Judd Gregg announced his retirement, New Hampshire looked like a great pickup for Democrats, especially considering they just won the state's other Senate seat in 2008.  Democratic Representative Paul Hodes is likely to be the standard bearer for his party, but Republicans just pulled the best candidate they could have in state Attorney General Kelly Ayotte.  Already, she polls as well or better than Hodes, given her statewide name recognition.  And while early poll numbers may be deceiving, New Hampshire is the most politicall conservative state in New England, and may not offer the opportunity that Democrats were hoping for.

Delaware - Tossup

I wouldn't normally put a state in the tossup category on the basis of just one factor, but Delaware seems to be an exception.  Joe Biden couldn't have lost an election there if he had tried, and the early indicators appeared that his son, Attorney General Beau Biden, looked set to carry on the family tradition.  But longtime at-large Republican Representative Michael Castle, surprisingly, polls way ahead of Biden.  Castle appears set to either run for the Senate or retire.  If he chooses the former, it will be an uphill battle for the younger Biden.  And that scenario is looking more and more likely.

Illinois - Likely Democrat hold

With embattled Senator Roland Burris retiring, the Democrats' field has cleared considerably, giving state Treasurer and Obama pal Alexi Giannoulis  a clear path to the general election.  Republicans drew probably the best possible candidate in their Illinois stable, moderate Rep. Mark Kirk.  Even with the stain Rod Blagojevich left on the Democratic Party in Illinois, it's still a strong blue state.  Plus, Kirk has never held a statewide office, while Giannoulis has.  But perhaps the biggest issue will be that Democrats will likely be willing to spend a lot of money to avoid the PR headache that would come with losing the incumbent president's former seat.

Pennsylvania - Likely Democrat hold

When Arlen Specter switched parties in April, he noted that he thought that the GOP platform was no longer reflective of the Pennsylvania electorate.  He probably read that right.  Republicans look dead set on nominating Pat Toomey, who is far to the right of the state's voters, which gave Barack Obama a crushing victory in 2008.  Specter polls way ahead of Toomey, as does Democratic Rep. Joe Sestak, who will challenge Specter in a primary matchup.  Whoever emerges from the Democratic primary will almost certainly win the general, but the primary itself will be an incredible battle to watch.

Missouri - *Leans Democrat pickup*

Kit Bond may have been the only Missouri Republican who could have won in 2010.  But with the longtime Senator retiring, Democrats look all but certain to add the seat.  Secretary of State Robin Carnahan- daughter of former Governor Mel Carnahan, and former Senator Jean Carnahan- has a healthy lead over all Republican challengers, including lontime Rep. Roy Blunt and former state Treasurer Sarah Steeleman.  With her name recognition and young face, she likely stays out in front long enough to hold off Blunt.

Ohio - *Leans Democrat pickup*

The GOP drew just about the best possible candidate they could in former OMB Director Rob Portman for the open seat race in Ohio to succeed retiring Republican George Voinovich.  Still, with all his experience, popularity, and conservative pedigree, he trails both Lieutenant Governor Lee Fisher and Secretary of State Jennifer Brunner by anywhere from 5-10 points.  That's bad news this early on.

Florida - Likely Republican hold

Democrats had a decent shot at taking another Florida Senate seat until Governor Charlie Crist got involved.  The moderate governor faces a challenge from conservative State Senator Marco Rubio, who is lagging in the polls currently.  The only way Democrats have any kind of shot with their apparent nominee, Rep. Kendrick Meek, is if Rubio does the unthinkable and upsets Crist.

Louisiana - Likely Republican hol

You'd think getting caught on a call-girl service's client list would cost you your job, but David Vitter appears to be weathering the storm, if for no other reason than that Democrats can't find a powerhouse candidate.  Without one- soon- Republicans will hang onto this seat.

There are a few other seats that could get more competitive if the right candidates get involved.  In North Carolina, Republican Richard Burr would be in trouble if every strong Democrat didn't keep passing on the race.  In the Colorado special election, Michael Bennet will be safe if the GOP can't manage to recruit anyone stronger.  In Oklahoma, Democrats have no shot at all unless term-limited Governor Brad Henry changes his mind and runs for the Senate. 

The seat that may surprise some people is New York, which likely won't get competitive even if Republicans manage to recruit their top guy, former Governor George Pataki.  With Chuck Schumer running for reelection, he's likely to have a coattail effect that will make up for whatever defeicit Kristin Gillibrand might be looking at down the road.