Romney, a former governor of Massachusetts and co-founder of the Bain Capital investment firm, leads slightly among likely Nassau and Suffolk voters -- 47 percent to Obama's 45 percent. Seven percent of respondents said they were undecided or refused to declare their pick, and 1 percent opted for a third-party candidate. The poll has a 3-point margin of error.
The results echo national polls that show a tight race leading up to the Nov. 6 election.
"This almost looks like a classic swing state," said Donald Levy, director of the Siena Research Institute, which polled 1,008 Long Island registered voters from Oct. 17 to 22, of which 958 were likely voters.
Despite the close race on Long Island, statewide polling figures released by Siena on Friday show Obama leading 59 percent to Romney's 35 percent, with 6 percent undecided.
While 49 percent of Long Island respondents had a "favorable" opinion of Obama, compared with 48 percent for Romney, the president received lukewarm ratings for his last four years on the job.
Asked to rate Obama's performance on five key campaign issues -- the economy, conflicts in the Middle East, health care, immigration reform, and Iran's nuclear program -- 57 percent categorized his job between fair and poor, with 44 percent rating his job between good and excellent.
"Even the voters who prefer the president at this point are not jumping up and down," Levy said. "They're not saying he's doing a good job. What they're saying is he's doing a good enough job."
Jon Cooper, a former Suffolk County legislator who served as the tri-state coordinator for the Obama campaign in 2008, said the results are reflective of voters nationwide who "are looking for compromise on even the most contentious issues."
"No one can deny we're making progress on the economy, but those folks still struggling are not going to be thrilled," Cooper said. "The question is whether Mitt Romney has provided real alternatives."
State Republican chairman Edward Cox said the figures indicate that Romney is gaining momentum not only on Long Island but also in key battleground states.
"There's great insecurity out there about the economy," Cox said. "People are still nervous, and they see Mitt Romney as a viable alternative."
With 71 percent of those surveyed classifying the economy as the most important issue of the election, Romney's business background worked to his advantage -- 50 percent of respondents said they were more inclined to support Romney's approach to the economy, compared with 45 percent for Obama. Five percent were undecided.
Ryan, who works part-time as a groundskeeper for the Crescent Club in Centerport, said his vote is based partly because he thinks "Obama is in over his head when it comes to the economy."
Health care ranked as the second most important campaign issue, with 19 percent selecting it as their top issue. While 48 percent of respondents favored a repeal of the Obama administration's health care plan, 48 percent said they were more inclined to support the president's approach on health care over Romney.
The tight race between the two candidates on Long Island signals winnowing support for Obama among independent and third-party voters and political moderates. Romney leads by 49 percent to Obama's 38 percent among independents and third-party voters, and respondents who call themselves political moderates were virtually split in their support -- 46 percent in favor of Obama to Romney's 45 percent.
Cliff Rawland, a 61-year-old registered Democrat from Inwood, who describes himself as a moderate, said he voted for Obama in 2008, but after struggling to find a job since being laid off as a private bus driver in 2010, he is undecided about either candidate.
"The economy is still bad under Obama, but I don't know that things will be much better under Romney," Rawland said.
In 2008, Obama won Long Island by close margins. In Suffolk, he defeated Republican challenger John McCain 52 percent to 47 percent, with 1 percent for other candidates. In Nassau, Obama won with 53 percent of the vote to McCain's 46 percent, with 1 percent for other candidates.