Forget 1994, Gallup’s demographic breakdown of their likely-voter model predicts.  The moderates actually reigned supreme in that Republican sweep, with the middle accounting for 48% of the turnout.  This time, conservatives make up 54% of the predicted turnout, twice as many as the moderates and three times as many as the liberals, and with independents breaking for the GOP, the amplitude of the wave could be enormous:

Gallup’s recent modeling of the vote for Congress finds 54% of likely voters identifying themselves as politically conservative, while moderates are in conspicuously short supply compared with recent midterms. Also, Republicans make up a larger share of the electorate in Gallup’s initial 2010 likely voter pool — greater than their 1994 share — than do Democrats, and the gap is even more pronounced once the leanings of independents are taken into account. …

The composition of likely voters appears to have become more politically polarized, with the proportions of conservatives and liberals expanding since 1994 at moderates’ expense. However, Gallup’s initial 2010 estimate of likely voters shows a particularly sharp jump in the percentage of conservatives, from 42% in 2006 to 54% today, and a decline in the percentage of moderates, from 37% to 27%.

This ideological change is accompanied by a concomitant shift toward Republicans, who have a nine-percentage-point advantage over Democrats in the likely voter pool: 39% vs. 30% at this point, one month before the elections. This exceeds the GOP’s five- and six-point advantages in Gallup’s final pre-election polls in 1994 and 2002, respectively, and is a reversal from 1998 and 2006, when Democrats slightly outnumbered Republicans.

Once the “leanings” of independents are taken into account, the majority of the 2010 electorate, 57%, identifies either as Republicans or as independents who lean Republican, compared with 39% identifying as or leaning Democratic. The previous high was 51% in 2002.

Gallup actually runs two different turnout models.  The first assumes a turnout percentage of about 40%, typical for a midterm election.  The other assumes a turnout of over 50%, where Democrats start to turn out more than expected to match the enthusiasm of Republicans and independents.  Even in that scenario, the GOP gets a 13-point edge in the generic Congressional ballot; in the 40% model, that lead expands to 18 points.  The analysis above applies to the 40% model.

Bear in mind that prior to this year, the biggest lead the GOP had in any generic Congressional ballot was five points, which came in 1994.  In that election, the split was 49/44 in the Gallup poll prior to the midterm election, while this year it’s 57/39, as noted above.  That 1994 election produced a net pickup of 56 seats in the House.

The election isn’t over yet, and plenty can happen in three weeks.  This model, though, could produce a political wave unlike anything seen in our lifetimes even if Barack Obama and Joe Biden can scold some more Democrats into making their way to the polling stations — and it bodes very ill for Democrats in states where early voting has already commenced.