The election is still a year away and pressing issues such as the health overhaul, the lagging economy and the future of the Afghan war could tip the balance. Yet, there are some little-understood forces that suggest a full repeat of 1994 is unlikely.

For the moment, all but nine House Democrats have said they are defending their seats, far more than in the 1994 cycle, when 29 incumbent House members in the party vacated their seats — and Democrats lost 22 of those spots. Incumbents stand a far better chance of hanging on in a political storm than do newcomers. In addition, Mr. Obama, for all his recent troubles, hasn’t slumped in popularity as far as President Bill Clinton did then, at least so far. And while Democrats’ fund-raising lead has slipped in recent weeks, they have built up an advantage in campaign cash.

Perhaps as important, Democratic leaders have warned lawmakers earlier this time to start preparing for a tough fight; in 1994, by contrast, even some prominent Democrats didn’t realize until late in the game that they were in trouble…

Individual Democratic candidates have built even bigger war chests on their own. The center’s figures indicate that Democratic House and Senate candidates have raised $97.4 million so far this cycle, compared with $59.5 million for Republicans, and have about $62.4 million more cash on hand. Still, one positive sign for Republicans emerged on the money front in recent weeks: The party’s national committees out-raised Democratic committees by $1.6 million in the month of August.