If Obama is elected and the Dems get the “Magic 60” to make their legislation bulletproof, then it is possible that they will be the most left-wing government ever, but not likely. If it does happen and they do tack way to the left, it will be two years at most before you will see a massive shift at the House back to the GOP. The dynamics are different today than in the 1930s and 1960s for three reasons.
1) In both the New Deal and the Great Society, you had a GOP that was in disarray and allowed the Dems to move to the left even with the presence of the South in the coalition. Throughout the 1930s and the 1940s the Republicans struggled to find their legs and their vision. They only provided a check on FDR’s and Truman’s legislation by working as a tag team with the Southern Dems. By 1946 they were coming out of it and gaining strength but were held back by internal conflicts between more conservative Taft supporters and more moderate Dewey supporters. They worked together to check some left-wing bills under Truman (most notably through their votes on things like Taft-Hartley, killing the OPA, and attempting to reign in the tax rates and capital outflow) but didn’t provide a national message that rallied the voters. Ike was an aberration who could have been elected on the Toga and Keg Party ticket but his GOP party building efforts were all contingent on his presence. When he left you still had the same factional conflicts which weakened the GOP in the 1940s. The party was stronger but still didn’t provide a check once they reset after Goldwater. They were still heavily divided ideologically. A number of the GOP senators at that time (e.g. Jake Javits and Hugh Scott) were more liberal than today’s Republicans and the Great Society was able to make it through both houses. The conservatism of today’s Republicans, even with the presence of people like Olympia Snowe) will limit the type of left-wing moves a government can make. If last month’s fundraising totals were accurate, McCain-Palin are reaching the voters. If the election is as close as everyone thinks it will be, the Dems in the House will not have the kind of mandate that Johnson pulled over Goldwater and FDR pulled over Hoover-Landon-Willkie-Dewey.
2) In the 1960s, the New Deal was viewed by many as a good thing. Many still do despite Amity Shlaes’ best efforts. Through Ike, the GOP had not been able to repeal many of the ND’s programs and by 1950 its leadership realized that Social Security, for example, was a permanent feature of America’s political landscape. The Great Society was a failure of eipc proportions and I think most Americans realize this. Some blame it on the war in Vietnam to be sure (and that was definitely one of the factors), but I don’t think the Great Society will generate the kind of nostalgia that LBJ capitalized on to push his plans through. A significant number of people will not view an expansion of government power as a solution and a return to better times. There will be grassroots resistance if Obama moves too far because we have been down that road before and it didn’t work out so well.
3) The conservative apparatus, both inside and outside of the party, will continue to function and will provide an effective counter to any far left legislation that is proposed. For every far left measure that passes, Right-wing think tanks, publications, and radio shows gain ammo for 2010. The reality and power of conservative institutions was on display in 2004 and, I think, will force an Obama government to govern as a centrist or else go to divided government in 2010 and possibly lose the White House in 2012.
This is all barring a catastrophic economic collapse which will change the political calculus, or Obama actually trying to govern like Eisenhower and build a non-partisan government to unite moderates of both parties against the extremists of both the left and the right. I don’t think either of those two will happen.