DENVER — In 2008, Colorado became a symbol of the changing politics in a region once firmly in Republican hands — and also of the grass-roots power and energy fueling President Obama’s candidacy. Today, the state embodies the uneasiness spreading throughout Democratic ranks as Obama struggles with major challenges and the 2010 mid-term election year approaches.Colorado has been one of the Democratic Party’s major success stories. Between 1968 and 2004, Republican presidential candidates failed to carry the state in only one election. Last year, Obama crushed John McCain in Colorado, part of a broader shift in the balance of political power in the Rocky Mountain West.Obama’s victory and earlier Democratic wins here have transformed the state. Early in the decade, Republicans controlled virtually everything — the governor’s office, almost all other statewide offices, the congressional delegation and both houses of the Colorado legislature. Today, Democrats are in control of all of those.A year ago, Denver enthusiastically hosted the Democratic National Convention, which culminated with Obama’s acceptance speech before more than 80,000 people at the Denver Broncos’ football stadium. Legions of volunteers, young and old, fanned out around the state throughout the fall to rally the vote for Obama’s campaign.Today, the energy that powered Obama to victory has begun to dissipate. Some of his supporters remain on the sidelines; others are, if not disillusioned, questioning what has happened to his presidency. As they look toward 2010, Democrats are nervous. Gov. Bill Ritter, appointed Sen. Michael Bennet and at least one Democratic member of the House are likely to face difficult election campaigns next year.Roy Romer, the former Democratic governor, called the state of play “very much tougher” for Obama and the Democrats now than a year ago. “The slippage is there, and it’s because things are tough and solutions aren’t easy, and they (voters) don’t see progress toward solutions,” he said.“The political environment is tough for Democrats, tough for incumbents, tough for all politicians,” Mike Stratton, a veteran Democratic strategist based in Denver, said a few days ago.The Obama of 2008 seemed perfectly attuned to a state known for its youthfulness, future-oriented outlook and positive spirit. If he struggled at times with older voters in Rust Belt states, he always found a welcome here in Colorado, easily defeating Hillary Rodham Clinton in the Democratic caucuses before cruising past McCain in the general election.Today, Coloradoans appear more downbeat. Anxiety has replaced optimism. The recession has changed habits and attitudes. Obama’s agenda has raised questions among independent voters because of its ambitious scope and potential impact on the deficit. His style has left some of his original supporters concerned about his toughness.Grass-roots organizers like Jeff and Gale Haley, who volunteered for the Obama campaign last year and are now helping to organize support for health care, say it is critically important for Obama to take a harder line in his effort to pass a health care bill. “I think he certainly realizes that if he loses on this one, that sets the tone for the rest of his administration,” Jeff Haley said.Bennet, who was touring northeastern Colorado last week, said: “We need to be able to demonstrate — the administration needs to be able to demonstrate, people that are running for office need to be able to demonstrate — that we’re up to those challenges and that we’re providing constructive policy solutions to meeting those challenges. If we can do that, we’re going to be OK. If we can’t do that, we’re going to be overcome by the anxiety that’s out there.”Bennet was the surprise pick to fill the vacancy left when the president nominated former senator Ken Salazar as Interior secretary. He came to the Senate with no experience in elective politics. When he was tapped, he was serving as superintendent of the Denver school system. Before that he was chief of staff to Denver Mayor John Hickenlooper and also had acquired private-sector experience with an investment company.Bennet has a quick mind and has impressed other Democrats as an innovative and sometimes out-of-the-box thinker. He has worked to learn how to be a politician, traveling the state so his constituents can get to know him and raising money as rapidly as he can. Still, given the state of the economy, he is far from secure in his seat, and Republicans see him as a vulnerable target.“Bennet has not solidified himself as an incumbent senator,” said Dick Wadhams, the Colorado Republican Party chairman.Bennet is preparing for a difficult general election campaign, but his most immediate problem is a likely primary challenge from Andrew Romanoff, a Democratic former speaker of the Colorado House.Romanoff was one of the leading candidates for the Salazar vacancy before Ritter tapped Bennet, and other Democrats see his challenge to Bennet as motivated more by personal pique than by principled differences with him. Whatever his motivation, Romanoff creates one more obstacle in Bennet’s path as he tries to win his Senate seat outright.Ritter also has problems. First and foremost is the challenge facing every governor this year and next: how to run a state in the middle of a recession that has created a sizable budget deficit.Colorado’s economy is far from the worst in the country, but Ritter, like other governors, has been forced to cut spending. In one of his most unpopular decisions, he has raised the fee for automobile registrations. He also has alienated organized labor. Some of his critics, including Democrats who will support him, say he has lacked the decisiveness needed in a time of big problems.For all the edginess among Democrats, Republicans have their own hurdles to overcome. The party faces primary contests for both governor and Senate. Republicans here must resolve some of the ideological schisms that reflect broader divisions nationally. Demographic and other changes have given the Democrats parity with Republicans in party registration, with the state now divided almost evenly among Republicans, Democrats and unaffiliated voters.Although Colorado has shifted from red to almost solidly blue in its representation, it remains a purple state politically, especially given the size of the unaffiliated vote that can shift with the tides. Some strategists say Democrats may have reached their high-water mark in 2008. What happens here over the next 14 months will show whether they can consolidate and solidify those earlier victories, or whether Republicans can begin their comeback.