President feels the heat as he struggles to inspire voters on the campaign trail

When President Barack Obama mentioned the Republican party convention on the campaign trail in Fort Collins, Colorado, and his supporters began to boo his opponents, he paused and went off script.

“Don’t boo. Vote. That’s the best response. Vote and get some of your best friends to vote,” he told the audience at a rally on a campus of Colorado State University.

The tone of urgency was notable. The 2008 version of Obama had no trouble getting people to go to the ballot box during his historic election win. But in 2012 it is a different game. Battered by the realities of four years in office and with a party base that often believes he has let them down, Obama is facing an enthusiasm gap as he prepares to rally Democrats at their nomination convention in Charlotte, North Carolina.

It will not be an easy task and his speech on Thursday night will be a test of whether Obama the president can rekindle the sort of emotion that saw Obama the candidate run one of the most remarkable campaigns of modern American history. “A lot of people feel that it has been politics as usual and there has been no fundamental change. It is a real problem for him,” said Professor Shaun Bowler, a political scientist at the University of California at Riverside.

That enthusiasm gap in the fight against Republican challenger Mitt Romney can be read in poll numbers. At this point in 2008, 63% of Americans viewed Obama favourably. Now it is 53%. It can also be seen at the rallies. Though Obama can still draw a crowd, the numbers, and the venues, are smaller than four years ago.

Commentators remark on a noticeably flatter atmosphere. It is an issue acknowledged in Obama’s speeches, where he makes cracks about his greying hair and refers to his famous “hope and change” slogan of the last campaign. “They’ll tell you that if you believed in change four years ago then you were foolish. They hope you’ll be discouraged and stay away [from the polls] this time,” Obama told a mostly student crowd in Iowa at another campaign stop.

Of course, talking about a problem is a surefire way to acknowledge that it exists. Though no one has to tell Bob Fulkerson about it.

Fulkerson is co-founder of the Progressive Leadership Alliance of Nevada, a group that campaigns on left-leaning causes in the vital south-western swing state. In 2008 Obama won Nevada by 12 points. Now it is a close-run race. As he knocks on doors throughout the state, Fulkerson can feel the difference. “He was a knight in shining armour. Four years later? OK, there is some disappointment,” he said. “We still have to fight like hell to get this guy re-elected.”

The reasons for the disappointment are twofold. First is the continuing economic malaise and high unemployment still gripping America. Though he came to power in the midst of an economic crisis, Obama has stabilised the situation rather than kick-starting a boom. That allows Republicans to attack his economic record. Second, there has been a series of policy disappointments.

Obama sent more troops to Afghanistan, failed to close the detention camp of Guantánamo Bay and his healthcare reforms are unpopular with both left and right. His curbs on Wall Street have been seen as weak and his administration as still too close to the banking industry.

The situation also explains the staggering level of negativity in the all-important “ad wars” flung at the Romney camp. Obama’s team, led by famed “hatchet man” David Axelrod, has assaulted voters in vital swing states with brutal takedowns of Romney. They have featured Romney singing off-key, speculated openly that he might not pay taxes and played dirty when it comes taking remarks out of context. A low point came when Democratic Senate leader Harry Reid speculated publicly that Romney might not have paid tax for a decade, even while admitting he had no idea if the allegations were true.

It is a long way from the sunny optimism of 2008. “This has been a dismal election campaign,” said Larry Haas, a political expert and former aide in the Bill Clinton White House. However, Haas believes that Obama still has key advantages such as the organisation left over from the 2008 campaign that will provide hard-to-beat numbers of boots on the ground. “The president built a very impressive operation in 2008 and he has spent four more years building it up. That will ensure he gets the maximum number of people out to vote,” Haas said.

Obama has also been helped by his opposition. The Republican nomination race was marked by bizarre and eccentric campaigns. When Romney emerged as winner it was as head of a conservative base yet to warm to him. He has been hindered by a lack of charisma, by his image as a wealthy financier and by his choice of hard-line social and fiscal conservative Paul Ryan as a running mate.

That is certainly what Fulkerson finds in the cities, suburbs and small towns of Nevada. While Obama and the Democrats may be a tougher sell this year, persuading people that they should worry about Romney and Ryan is easy. “The stakes are too high to give up now,” Fulkerson said. “Except it’s not hope and change any more, it is more hope and fear.”