Take a step back and consider how much the political climate has changed over the past year.

Just 12 months ago, Democrats were blissful, celebrating their White House victory plus the expansion of their majorities in the House and Senate. Republicans were sullen, contemplating their total removal from power.

Today, Democrats fear that their edge in the Senate could be halved next November and fret that their hold on the House is not secure. In the past month, four Democrats representing tough House districts have announced their intention to retire. Now Republicans are pinching themselves at the idea that their time in the wilderness might be much briefer than they feared.

In the House, the Democrats' grip appears to be holding. The Cook Political Report currently rates all but 40 of the Democrats' 258 House seats as either "solid Democratic," meaning totally secure, or "likely Democratic," meaning not seriously challenged today but potentially competitive.

To put it another way, as things stand now, Republicans could win every competitive House race and still come up one seat short. That won't be the case, however, if there is further erosion in the ranks of the solid and likely Democratic seats. Although Democrats can take some solace from the fact that no party has ever lost every single competitive House race, none of the four lawmakers who have recently added their names to the retirement list -- Brian Baird of Washington, Bart Gordon of Tennessee, Dennis Moore of Kansas, and John Tanner of Tennessee -- was considered particularly vulnerable a year ago.

For Republicans to take control of the House, more Democrats in swing districts would have to retire. There will be more, but how many?

If 10 or 12 more seats rated as solid or likely Democratic shift to the "lean Democratic" or "toss-up" columns, the fight for control will become much more serious. Washington is awash in rumors of other veteran Democrats contemplating voluntary exits. Some serve in safely Democratic districts, but others represent places not unlike the districts of Baird, Gordon, Moore, and Tanner. Also helping the GOP is its best House recruiting in a long time. A crop of strong candidates will help Republicans win more than their share of contests if the political environment remains what it is today.

Winds that began shifting against Democrats around the end of June are transforming their party's potential problems into real ones.

Winds that began shifting against Democrats around the end of June, during the House cap-and-trade vote and the beginning of the health care debate, are now transforming their party's potential problems into real ones. That change is causing predictable talk of a 1994-style Republican landslide strong enough to flip the Senate. That talk, though, is just so much hot air.

Anyone with the slightest knowledge of the Senate's 2010 lineup of contests couldn't take such talk seriously. For Republicans to seize the Senate, they would have to hold all six of their open seats, which is quite plausible. All 12 of the GOP incumbents up for re-election would also have to win, which is quite likely. The Republicans would then have to pick up the Delaware and Illinois open seats that Democrats now hold -- a feat that is not difficult to imagine.

However -- and this is where the going would get rough for the Republicans -- they would need to defeat Michael Bennet in Colorado, Barbara Boxer in California, Christopher Dodd in Connecticut, Kirsten Gillibrand in New York, Blanche Lincoln in Arkansas, Harry Reid in Nevada, and Arlen Specter (or Joe Sestak if he wins the primary) in Pennsylvania, plus Republican Gov. John Hoeven of North Dakota would have to run and beat Byron Dorgan.

No party in history has ever run the table that completely. And even then, the GOP would come up one seat short.

The fragility of the Democrats' Senate majority is visible, though, if you look toward 2012, when 23 Democratic seats will be on the line compared with just nine Republican ones, and ahead to 2014, when 20 Democratic seats but only 13 Republican ones will be up for grabs.

Just as much has changed in the past year, much could change in the next. What the past tells us is that it takes a truly major event -- such as the 9/11 attacks of 2001 or the 1998 impeachment of President Clinton -- to improve the fortunes of the president's party going into a midterm election. Only one thing seems certain: 2010 won't be dull.

This article appeared in the Saturday, December 19, 2009 edition of National Journal.

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