Much can change, nationally and locally, before Nov. 2, 2010. But perhaps the most politically salient thing is unlikely to change: high unemployment. The Wall Street Journal recently reported that the economy, which has lost 7.2 million jobs since the recession began in December 2007, must create 100,000 a month just to match population growth. Joseph Seneca, a Rutgers economist, estimates that even if job creation were immediately to reach the pace of the 1990s — an average of 2.15 million private-sector jobs were added each year, double the pace of that between 2001 and 2007– the unemployment rate would not fall to 5 percent until 2017.

September’s 9.8 percent unemployment rate was the worst since June 1983. But robust growth began then, and just 17 months later Ronald Reagan came within 3,800 Minnesota votes of carrying all 50 states. Reagan, however, was reducing government’s burdens — taxes, regulations — on the economy. Obama is increasing them.

The possibility of Republican gains, especially in the Senate, helps explain why Obama is in such a rush to remake the nation and save the planet. His window of opportunity could be closing.