Charlie Cook, still the best congressional election prognosticator there is, has entered his biennial weatherman phase. When Cook speaks of an ill-wind blowing for a particular party, that party is usually in trouble.

Cyclical and seasonal forces are conspiring against Democrats, he writes. Cook identifies two: Since the House of Representatives is largely ideologically and geographically sorted out (and because that sorting favors Republicans), Democrats are overexposed, having done better than Republicans in 2012. In the Senate, as Cook notes, if a party did well six years ago, it is likely to have more chances to lose seats the next time those seats are up. These two factors alone should mean that Republicans have a shot at taking control of the Senate and that Democrats have virtually no chance of regaining control of the House. The deep structure of politics is hard to change.

But beyond these forces, there are a number of others that are blowing in the face of Democrats, some of them quite strongly. They are unique to this moment in politics and history. As Cook notes, President Obama's relative unpopularity all but makes it certain that the Democratic base is unlikely to find itself enthusiastic. A few other conventional metrics work to the Democrats' favor. The economy is getting better, slowly, and personal incomes are rising. But I'd wager that Washington has cast so big a shadow over perceptions about which party is doing more to help the economy that people think the country is kind of on autopilot.

Let's look at some others.

1. There are a number of strong Republican Senate candidates, so Democrats will have to distribute their resources to more states. Democratic donors are not enthusiastic about the elections, because they read prognosticators like Charlie Cook, and when they read Charlie Cook, they tend to believe him. (This is why the White House will never admit how precarious the situation in the Senate actually is for Democrats; they would kill off fundraising even more.) The basic point is that Republicans can raise what they need. Democrats will have to struggle to match them.

2. The Republican Party has made significant investments in technology and voting targeting. The Democrats still do it better, but their relative advantage has decreased. (The GOP is not investing very significantly in the future of political consulting talent, and this will be a problem later on.)

3. The Big Democratic Argument about government is that it can work. Right now, they've got nothing to base that argument on. So they are, quite naturally, trying to make the election a referendum on the evil Republicans, like the Koch brothers, who are corrupting American political campaigns. (This is how they get out the base.) Unfortunately, this type of argument almost never works. It just doesn't. It works in focus groups with Democrats, but it doesn't translate into votes.