Support for the Boston Olympics has inched upward, but the city’s bid for the 2024 Summer Games remains unpopular and residents are deeply worried about cost overruns, according to a new poll.
Forty percent of Boston-area residents now support the bid, while 50 percent oppose it, according to the WBUR survey of registered voters who live within or straddle Route 128.
For backers of the Boston Olympics, that is a slight improvement from last month, when 36 percent supported the bid and 52 percent opposed it.
But enthusiasm for the effort remains well below where it was in January when the US Olympic Committee chose Boston to be the American bidder for the Games. Back then, 51 percent supported the bid and 33 percent opposed it.
Within the city of Boston, support for the Games is higher. For the first time since January, more Boston voters (47 percent) support the bid than oppose it (41 percent).
If given the choice, more Boston-area residents (36 percent) would prefer the Games be hosted in a European capital than in Boston (25 percent).
Public support for the Games has become a major preoccupation of Boston 2024, a private group of prominent executives and high-powered former political figures who are pushing the bid.
Initially opposing any vote on the effort, they recently reversed course and would back a statewide referendum in 2016.
If the referendum fails to win majority support in Massachusetts or in Boston, Boston 2024 has said it would drop the bid. Mayor Martin J. Walsh, who is also backing the bid, has said he would like support to reach 70 percent in the city.
One key concern for residents, according to the poll, is cost overruns. Boston 2024 has promised an affordable, efficient Olympics, but 90 percent of respondents said they think the Games are very likely or somewhat likely to cost much more than estimated.
Boston 2024 has also asserted that the Olympics would spur construction of affordable housing, but 72 percent of Boston-area residents do not think that is likely to happen.
Residents were more hopeful that the Boston region would benefit economically from hosting the world’s largest sporting event. About 52 percent of those polled said that an economic boost was likely while 44 percent said it was not likely.
Residents were about evenly divided on whether they think the Olympics would leave Boston with a better transportation system. About 48 percent said that better public transit was likely while 46 percent said it was not likely.
The survey of 509 registered voters was conducted April 10 to 13 and has a margin of error of 4.9 percentage points.
Michael Levenson can be reached at michael.levenson