LITTLE ROCK — Former natural gas company executive Sheffield Nelson on Tuesday suspended indefinitely his drive to put a proposal to raise the state severance tax on natural gas before voters in November.

But he left the door open for possibly resuming signature-gathering.

Nelson, who has to make a more than 40,000-signature deficiency by Aug. 20, said he was leaning toward ending the effort altogether until two supporters offered him $50,000 to continue the campaign to qualify the measure for the ballot.

He said funding isn’t an issue, but that he would talk with other supporters about the campaign and hopes to make a final decision within a week.

"What I am going to do (Tuesday) is suspend the gathering of signatures … until we can analyze where we are and where we think we ought to go," he told reporters at a news conference.

Nelson’s Committee for a Fair Severance Tax submitted 69,717 signatures to the secretary of state’s office on July 6, of which Secretary of State Mark Martin determined 21,347 were valid signatures of registered voters. The group needs 62,507 valid signatures to qualify the proposal for the November ballot.

"I said at the time it was going to be a mountain to climb, not a hill, if we tried make up 40,000 signatures," Nelson said Tuesday. "I honestly felt we would be 10,000 or 15,000 short, at the most."

Nelson said he was disappointed in the canvassing process and felt like some of his paid canvassers did not try hard enough and lied in their collection efforts.

He said he would like to see the Legislature consider changes to the referendum process, including reducing the number of signatures required.

"I think it’s too high," he said. "The whole thing needs to be adjusted."

During the news conference, Nelson also said he has received notification from the U.S. Securities and Exchange Commission that it will review concerns he has raised about two gas companies working in the Fayetteville Shale play region that are backing opposition to his proposal.

Southwestern Energy and XTO Energy Inc. a subsidiary of Exxon Mobil Corp., are two of the biggest contributors to Arkansans For Jobs and Affordable Energy, an Arkansas State Chamber of Commerce-led group formed to oppose Nelson’s severance tax hike. The group has raised nearly $1.8 million and spent $1.6 million.

According to Arkansans For Jobs and Affordable Energy contribution reports on file with the Arkansas Ethics Commission, Southwestern has contributed $700,000 to the group as of July 16, and XTO has contributed $450,000.

Nelson sent a letter to the SEC in June alleging that Southwestern Energy Co. and XTO Energy Inc. "participated in disseminating misinformation to the general public" in Arkansas, which includes some shareholders of the companies, concerning the impact of his proposal to raise the severance tax on natural gas.

He also contended in his letter that the companies had not made public disclosures to all their shareholders about the issue.

Tamara Brightwell, senior special counsel to the director, in a letter to Nelson dated July 20, said the agency "will carefully evaluate the information you have provided and will consider the information in light of our authority and responsibilities under the federal securities law."

Jeff Neu, public and government affairs adviser with XTO Energy, said the company does not believe this current debate merits an SEC filing.

Neu said if voters approved Nelson’s tax hike proposal, "a significant severance tax increase would impact our cost to drill in Arkansas, and such cost increases will be taken into account when making future investment decisions."

Officials of Southwestern did not immediately return calls seeking comment Tuesday afternoon.

Also Tueday, secretary of state’s office spokesman Alex Reed said Nancy Todd’s Poker Palace LLC, which is working to get an amendment on the ballot that would allow casinos in four counties, came up short in its collection efforts.

Reed said Nancy Todd turned in 80,373 signatures, but only 23,616 were verified. Backers needs 78,333 valid signatures to qualify for the ballot. It has 30 days to try to make up the 56,756-signature deficit.