“I think it’s very significant; they’d been losing ground and they turned it around,” he said.  Republicans now control the executive and legislative branches in 10 states, down from 12 before the election. They did gain control of the Montana House by one vote and fought to a tie in the Montana and Oklahoma Senates, which had both been under Democratic control.  Twenty-four states are now split, and one, Nebraska, has a nonpartisan legislature.  Control of state capitols has effects far beyond local laws. The parties running the statehouses will control redistricting for the 2010 Census and can groom rising politicians for national office.  Political analysts said an equally important nuance was how the shift played out state by state for the Democrats. The party added five governors — in Arkansas, Colorado, Massachusetts, New York and Ohio — from seats held by Republicans who had chosen not to run or were barred by term limits.  Democrats picked up a sixth seat in Maryland, where Mayor Martin O’Malley of Baltimore edged out Gov. Robert L. Ehrlich Jr.  That shifted the advantage in governors to Democrats for the first time since 1994. The Democrats now control 28 governors’ seats to the Republicans’ 22. Before Election Day, those numbers were reversed.  The legislative gains, by contrast, were concentrated in the Midwest, where Democrats picked up about 104 seats, along with control of both chambers in Iowa, the Indiana House, the Michigan House and the Wisconsin Senate, and in the Northeast, where their net exceeded 140 lawmakers.  About 67 Democratic seats were added in the West.  In Arkansas, the Democrats gained control of the governor’s office with the election of Attorney General Mike Beebe and kept control of the Legislature. That gave the party unified control for the first time since 1994. Gov. Mike Huckabee, a Republican, was barred from running by term limits.  In Iowa, Chet Culver will replace a fellow Democrat, Gov. Tom Vilsack, who chose not to seek a third term. In addition to keeping the governor’s office in Democrats’ hands, the party took control of both chambers of the Legislature.  Democrats had not controlled the legislative and executive branches of government under the Capitol Dome in Des Moines since 1964. And before Tuesday, the State Senate was evenly split between Republicans and Democrats, and the House was under Republican rule.  New Hampshire accounted for more than 80 new Democratic lawmakers, bringing the state more firmly into line as a party bastion than any time since just after the 1870’s, when Democrats last ran the House, Senate and governor’s office, according to the New Hampshire Political Library, a nonpartisan education group in Concord.  “The state has been becoming more Democratic over last 20 years,” said Andrew E. Smith, an associate professor of political science at the University of New Hampshire. “But this swing is a real tidal wave.”  Democratic lawmakers in Maine also surged, especially in the House, where they went from a one-vote majority, 74 to 73 with four independents, to a 91-to-51 majority. In Oregon, the shift was smaller, but the effect was huge. A shift of four House seats, with two races undecided on Wednesday, along with the re-election of Gov. Theodore R. Kulongoski, gave Democrats control of the Legislature and governor’s office for the first time since 1992.  In Colorado, Bill Ritter, a Democrat and former prosecutor in Denver, will succeed a Republican, Gov. Bill Owens, who could not run because of term limits. Mr. Ritter will be working down the hall in Denver with many more Democrats in the Legislature than Mr. Owens ever did.  Democrats gained narrow control of the Legislature in 2004, and the vote on Tuesday expanded the margins of their power from a one-vote majority in the Senate to perhaps four votes — one seat was undecided — and from a five-vote majority to, perhaps, a 12-seat majority in the House, with one undecided seat there.  A political scholar who has tracked Colorado politics for years said he thought that the gains were less about a new Democratic message and more about reaction against the old Republican one. The expert, Robert D. Loevy, a professor of political science at Colorado College in Colorado Springs, said the election illustrated a core shift on where the parties obtained votes. The well-educated, affluent close-in suburbs of Denver, Professor Loevy said, are shifting to Democratic from Republican.  “This used to be the backbone of the Republican Party in Colorado,” he said. “But the rise of social conservatism in the Republican Party — pro-life, anti-stem cell — has alienated large numbers, and that’s the group that has abandoned the Republicans more than any other.”  A chart on Thursday about political party control in federal and state government misstated the number of states where Republicans control both chambers of the legislature and the number of states where neither party controls both chambers. Republicans control both chambers in 15 states, not 10. Neither party controls both chambers in 10 states, not 16.  A version of this article appears in print on , on Page P1 of the New York edition with the headline: In Statehouses, Too, Democrats Post Sizable Gains. Order Reprints| Today's Paper|Subscribe
The party’s victories in statehouses, combined with the six new Democratic governors, have given the Democrats one-party government in 15 states.