(CNN) - Four days before a crucial special election for a House seat, a new poll suggests the Democrat in the race is gaining momentum.
A Siena College Research Institute poll of likely voters in New York's 20th congressional district indicates that Democrat Scott Murphy leads Republican Jim Tedisco by a 47 percent to 43 percent margin. That's a switch from two weeks ago, when Tedisco had a four point lead in a Siena poll and from one month ago, when Tedisco led by 12 points.
But the poll also indicates that by a ten point margin, 45 percent to 35 percent, voters think Tedisco will win.
"Taking the poll's sampling error into account, this race is neck-and-neck," says CNN Polling Director Keating Holland. "The tricky task for any pollster is trying to figure out who will actually vote in a special election for a local seat in an odd-numbered year. Likely voter models are generally based on historical voting patterns, but there is no history to fall back on in a race like this."
Murphy is a venture capitalist and Tedisco is a New York State lawmaker and ranking Republican in the State Assembly.
Both are running to replace Democrat Kirsten Gillibrand, who gave up her House seat after New York Gov. David Paterson appointed her to the U.S. Senate in January, to replace Hillary Clinton, who stepped down to serve as Secretary of State.
Gillibrand first won election to the seat in 2006 and was re-elected last November, in a moderate to conservative district that Republicans used to dominate.
The special election is scheduled for Tuesday.
Both the Democratic and Republican national party organizations and congressional campaign committees in the House of Representatives have pumped resources into the race.
The Democratic National Committee on Friday began running a television commercial in the district that uses visuals of Barack Obama and Murphy together on the screen and touts the president's support of the candidate. Earlier this week, the DNC went up with a radio spot in which Vice President Joe Biden voices his support for Murphy.
Republican have also flooded the airwaves in upstate New York with ads supporting Tedisco. President Obama's stimulus plan and even the controversy over AIG bonuses have become issues in the contest. Many political analysts see the race as an early referendum on how the Obama presidency has performed so far when it comes to the economy.
"Obama has endorsed the Democrat, so he can't run away from the results if the Republican wins," Holland says. "But local races often turn on local issues and the public perception of the two people on the ballot."
The Siena College Research Institute poll was conducted March 25-26, with 917 likely voters questioned by telephone. The survey's sampling error is plus or minus 3.2 percentage points.