BOSTON – Supporters of a proposal to bring casinos and video slot machines to Massachusetts abandoned their efforts Thursday, opting to withdraw the amendment from a Senate jobs bill.

“We will pull this. It will not be part of the economic stimulus package,” said Sen. Brian Lees, R-East Longmeadow.

Lees acknowledged that backers of the plan failed to win enough support in the Senate, where lawmakers had come under increasing pressure from both supporters and opponents of expanded gambling.

On Wednesday night, Lees had described support for the plan in the Senate as “50-50” with about 10-12 senators adamantly opposed to the proposal.

Senate critics of the plan hailed the decision to pull the proposal, saying the social costs of expanded gambling outweighed any economic benefits.

“In my opinion the members in this body showed the best leadership. I think this is a proud day for the members of the Senate,” said Sen. Susan Tucker, D-Andover, a gambling opponent. “When you start subtracting the cost of expanding gambling in this state, the costs are staggering.”

Sen. Michael Morrissey, who scrambled throughout the night Wednesday trying to hammer out a compromise version of the plan, said the proposal would have raised hundreds of millions in additional revenue for the state.

“This idea is not going away,” said Morrissey, D-Quincy. “I hope you keep an open mind in the future.”

Under Lees’ original amendment, each of the state’s four racetracks would have been able to install between 1,000 and 1,500 video slot machines.

In addition, the amendment would have allowed two stand-alone casinos, one in Bristol County and one in either Hampden or Worcester counties.

Lees said he was disappointed that the Senate did not opt to debate the issue. He said those morally opposed to gambling should push to eliminate scratch tickets, Keno and the Lottery.

“As leaders we have to be willing to stand up, have a healthy debate and take a vote,” he said.

Other senators said they simply didn’t have enough time to review the amendment, which was filed on Tuesday.

Few predicted that the issue of casinos is dead forever.

“We will have this discussion another day whether it will be the next budget cycle or in a few years or next year if the economy doesn’t improve,” Lees said.

The proposal was offered as an amendment to a $115 million Senate economic stimulus package designed to help jump-start the state’s flagging economy. The Senate approved the package minutes after Lees withdrew the gambling amendment.

Senators also had kept a close eye on Maine, where voters on Tuesday soundly rejected two Indian tribes’ proposal to build a $650 million, Las Vegas-style resort casino there.

While ruling out a casino, Maine voters decided to allow slot machines at the state’s commercial harness racing tracks in Scarborough and Bangor.

Some lawmakers suggested that Massachusetts should follow Maine’s lead and place a nonbinding ballot question regarding casinos before voters.

“My suggestion is that we seriously consider putting this on the ballot next November,” said Sen. Brian Joyce, D-Milton. “We would certainly get the will of the voters. We would find out what our constituents want.”