GOV. MARTIN O’MALLEY (D), tipping his hat to Maryland’s good-government crowd, included what sounds like a stern ban on campaign contributions by the gambling industry in his bill to expand gambling in the state. In the real world there’s very little the state can do to limit the clout of big casino operators, whose influence is already at work in state politics, in local governments and on the airwaves.

That clout is on vivid display this week in Annapolis as state lawmakers, in many cases disrupting their summer vacations, were summoned for a special legislative session on gaming. More than a few of them have observed that it’s hard to imagine any other industry with the muscle to force such a meeting; in fact the debate in Annapolis seems largely a fight between competing squadrons of well-heeled lobbyists. Notwithstanding the lofty rhetoric about job creation, it can be hard to discern the public interest in such an environment.

Mindful that the state has started to seem a captive of gambling interests, Mr. O’Malley’s draft legislation includes language banning contributions from them to state candidates, campaign committees or political parties. This is meant to insulate Maryland’s office-holders and political campaigns from the corrosive power of MGM Resorts, Caesars Entertainment and the industry’s other power players.

One problem is that the ban singles out a single industry for what looks like discriminatory treatment; that may not pass constitutional muster. If Maryland prohibits contributions from gambling interests, why do alcohol companies get a pass, or utilities, or any other regulated industry?

Even if constitutional, the ban probably will not cramp big gaming companies, which explains their silence on the matter. While the bill would ban contributions to political parties, candidates and campaign committees, it would not, and cannot, stop corporations from spending independently to influence public debates and elections.

One particularly easy way to skirt the measure, if it becomes law, is for gambling concerns to give money to nonprofit, tax-exempt organizations, which cannot be forced to reveal their funding sources. That exemption has been at work in recent weeks in competing volleys of television ads in the Baltimore market, some urging the expansion of gambling in Maryland, some condemning it. According to the Baltimore Sun, the two sides have spent more than $1 million in recent weeks on the ads. But it’s unclear who is paying precisely how much for the ads.

Given the gambling industry’s deep pockets, it’s unsurprising that the main debate over the governor’s bill has focused on how much to cut taxes for existing casinos in order to protect them from the additional competition posed by introducing a new casino in Prince George’s County. The governor and state Senate favored cuts up to about 17 percent. The House, which had previously fretted about cutting taxes for gambling titans after raising them this year for ordinary Marylanders, suddenly favored tax cuts reaching up to 25 percent.

It’s a little late to be worrying about limiting the political influence of one very rich industry in the state. On that count, the cards have already been dealt.