One year ago today, as the returns came in showing then-Sen. Barack Obama (D-Ill.) had trounced Sen. John McCain (R-Ariz.) in the presidential election, it seemed the world was at Obama’s feet.

Republicans were reeling under fresh losses in the House and a string of Senate defeats that left their Conference at 41. It would soon dwindle to 40.

“Yes we can,— Obama repeated that night, reviving the campaign slogan that had helped usher him to power.

But the Democratic ascendancy has been complicated for Obama, resulting in mixed success on Capitol Hill.

Obama walked into the White House with high expectations from Congress. Members were confident their former Senate colleague would have success passing his agenda given his experience under the Dome. And, unlike his predecessor, President George W. Bush, Obama had ready-made relationships with lawmakers that could prove critical.

Bush was often accused of taking a “my way or the highway— approach to working with Congress. Obama vowed to break that trend, saying early on he would work as an equal partner with the House and Senate.

But 11 months into his tenure, Obama hasn’t been able to use his alliances and experience to enact his top priorities.

The president has scored several important victories, signing bills to expand the State Children’s Health Insurance Program, provide Cash for Clunkers, add a $787 billion jolt of stimulus to the economy, expand hate crimes laws to include gays, as well as sign new equal-pay legislation and a bill creating added restrictions on credit card companies.

But the key issues he campaigned on — health care reform, cap-and-trade legislation and immigration — have been delayed amid Democratic infighting. The drama contrasts with the GOP discipline that propelled Bush’s top priority in his first year, a sweeping tax cut bill that was opposed by only one Republican in either the House or Senate, Bush’s GOP primary opponent, McCain.

“There’s a lot of diverse beliefs and opinions within the Democratic caucus,— said Sen. Ben Nelson (D-Neb.), a key moderate. Nelson cited Will Rogers’ famous remark: “I’m not a member of any organized party. I’m a Democrat.—

Moderate Democrats in the House and Senate are having trouble with both the government insurance option Obama touted during the campaign and the high cost of the health care reform bill. Legislation that Obama and Congressional leaders promised would be done by Oct. 15 now will be a Christmas present for the president, at best.

Obama may be faced with an even more acrimonious divide on the energy bill, particularly if moderate Democrats end up casting tough votes for health care reform.

Senate Finance Chairman Max Baucus (D-Mont.) and Environment and Public Works Chairman Barbara Boxer (D-Calif.) hope to avoid a showdown between the two committees that will be crafting legislation. Baucus and other moderates have concerns with the more liberal legislation emerging from Boxer’s panel.

Asked if 2010 was the time for the Senate to do cap-and-trade legislation, Nelson signaled tough times ahead: “From my standpoint, it may never be the time to do cap-and-trade legislation.— But he added that perhaps just “cap— legislation could work.

Immigration reform is not yet on the radar.

A year later, the triumphant slogan of the 2008 campaign has, in some cases, given way to the reality of governing.

Nelson noted that Obama is governing in a far tougher economic climate than he campaigned under, suggesting that his promises were harder to fulfill. Indeed, Democrats from moderate states and districts are being forced to vote on an expensive health care bill just months after adding billions to the deficit by passing the stimulus.

Sen. Amy Klobuchar (D-Minn.) sounded a similar theme, noting that Obama himself has said he would rather not be juggling so many balls at once, including the economy and the need to fund and fight two wars. In “normal times,— she said, the smaller victories he has won might loom larger.

But one senior Senate Republican aide said Obama has bitten off more than he can chew, and that he is overreaching on the issues he is trying to tackle, making it difficult to corral his whole caucus behind him.

“It reminds me of the story of the dog holding his bone and looking at his reflection in the pond, and then trying to grab the bone he sees, only to lose the one he actually has,— he said.

But Sen. Benjamin Cardin (D-Md.) asserted that Democrats have “a broader tent— than Republicans, making it inherently difficult to bring them together.

And Sen. Byron Dorgan (D-N.D.) argued that issues like health and energy are “very controversial— and resistant to consensus.

“Unity is a little more than you can hope for in the United States Congress,— Dorgan said. “I think the president has gotten a lot of his agenda through,— he added.

Sen. Carl Levin (D-Mich.) bristled at the very question. “There’s been a heck of a lot of unity, particularly when you look at the complexity of the issues,— he said.