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.

“Republicans have more chambers today than they have ever had in the history of the party,” said Tim Storey, an analyst at the National Conference of State Legislatures. “So they are in a dominant and historic position of strength in the states.”

The Democratic losses reflect a political realignment that began before Mr. Obama’s election and has accelerated since he took office, in which the electorate is increasingly polarized, and the partisan divisions of presidential politics are felt at all levels. The result has been a resurgence of Republican political power in governor’s offices and state legislatures, giving them the ability to draw districts and create voting rules that will benefit their party for many years to come. It has also meant a hollowing out of the roster of potential Democratic candidates for major races, knocking out candidates like Mr. Edelen, who drew national attention after video footage of one of his speeches aired on MSNBC.