While Mr. Obama’s 2008 election helped usher in a political resurgence for Democrats, the president today presides over a shrinking party whose control of elected offices at the state and local levels has declined precipitously. In January, Republicans will occupy 32 of the nation’s governorships, 10 more than they did in 2009. Democratic losses in state legislatures under Mr. Obama rank among the worst in the last 115 years, with 816 Democratic lawmakers losing their jobs and Republican control of legislatures doubling since the president took office — more seats lost than under any president since Dwight D. Eisenhower.