ST. PAUL — A leading Democratic state lawmaker said Wednesday he is growing more concerned about the reliability of tax revenue from electronic gambling machines that is supposed to help pay for construction of a new Minnesota Vikings stadium.

“I’m more concerned than I was before the hearing,” said Rep. Joe Atkins, DFL-Inver Grove Heights, after the House Commerce Committee — which he chairs — met to review the recent rollout of the electronic pull-tab games in bars and restaurants.

Tax revenue from those games is supposed to fund the state’s $348 million share of the $975 million Vikings stadium slated for downtown Minneapolis. But the tax revenue from the games, which started to become available in September, fell short of projections by $18 million through the end of 2012: while $35.2 million was projected to come in, the games returned only $17.2 million in tax revenue.

Backers of the new games said they need time to get more popular and expand to other bars.

“We would ask for your patience,” said Allen Lund, executive director of Allied Charities of Minnesota. Legal gambling in bars is operated by Minnesota charitable organizations, from youth sports clubs to veterans groups. “When all the distributors who want these products have it to sell, those numbers will go up exponentially. If we could get some patience, we would appreciate it.”

Atkins, who voted for the Vikings stadium plan when the Legislature approved it last spring, pointed out that lawmakers have only a few months if it becomes necessary to retool the bill.