'What we know in a wave election is, the losing side is discouraged and fails to show up at the polling places,' said Democratic pollster Peter Hart.

From The Wall Street Journal:

Republican challengers are suddenly threatening once-safe Democrats in New England and the Northwest, expanding the terrain for potential GOP gains and raising the party's hopes for a significant victory in next month's elections.

Some Democrats are signaling the potential for a rout, particularly in the House. A new survey by Democratic pollster Stanley Greenberg gives Republicans a six-point edge, 49% to 43%, when likely voters are asked which party they support in House races. That's a margin pollsters generally believe foreshadows large gains. "If the election were held today, it would produce a very unhappy night" for the Democrats, he said.

Nonpartisan handicappers say the GOP appears all but certain to gain about 30 House seats, largely from conservative or depressed districts in the South, Northeast and industrial Midwest. Pennsylvania, Ohio and New York look particularly vulnerable.

Now, pollsters and analysts say the pressure building in liberal corners of the country points to the potential for a so-called wave election, similar to the drubbing Democrats took in 1994. That could deliver a huge turnover in the House.

Democratic voters remain less interested in the race, a big factor behind the party's woes. The latest Wall Street Journal/NBC News poll found 66% of Republicans reporting intense interest, versus 52% of Democrats.

"What we know in a wave election is, the losing side is discouraged and fails to show up at the polling places," said Democratic pollster Peter Hart, co-director of the Journal poll. In recent weeks, "the crest appears to be going higher and higher with few signs that it will abate."