When I held my nose and endorsed expanded gambling in Maryland in a column two weeks ago, I cited a single reason: A big new casino at National Harbor would help the Prince George’s County economy.

Now I’ve got a second, admittedly petty rationale. A “yes” vote on Question 7 on the November ballot would justly humiliate Penn National Gaming, the giant casino company that has funded a massive advertising campaign against the proposal.

Maryland referendum primer

I would get a kick out of seeing Penn National humbled for its hypocrisy. It’s already spent more than $25 million for ads criticizing Maryland gambling on purportedly public-spirited grounds. The company’s true goal is to block competition for its existing, highly profitable casino in Charles Town, W.Va.

However, I have to concede that Penn National’s effort has been remarkably fruitful. Supporters and opponents of Question 7 credit the ads for a dramatic drop in popular support for gambling in Maryland since 2008. That’s when a landslide victory in an earlier referendum okayed opening five casinos with slot machines.

Today, a new Washington Post poll shows that Free State voters are evenly divided on the proposal to open a sixth casino in Prince George’s, and to permit live table games such as blackjack and roulette. Nearly two-thirds of those surveyed said they had heard or seen “a lot” of advertisements about the topic.

Moreover, even we Question 7 backers must acknowledge that voters are right to be skeptical that expanded gambling would yield all the potential benefits described by supporters. Penn National’s campaign has been especially effective in hammering the theme that government can’t be trusted.

It’s working partly because many original promises for slots in 2008 have come up woefully short. (My conscience is clear because I voted against gambling the first time around.)

In particular, advocates said four years ago that slots gambling would eventually yield more than $600 million a year for Maryland education. That hasn’t happened, partly because only three of the promised five casinos have opened. In the past three fiscal years, according to the supporters’ own mailings, the total gaming revenue for schools has totaled $185 million.

Penn National’s ads have emphasized, accurately, that this year’s casino proposal would not necessarily add money for schools in the future on top of increases that have already been promised.

Question 7 supporters stress instead that the new casino money would help pay for those planned increases in education spending. The gambling revenue would thus relieve pressure on the state to raise taxes or cut services other than education to satisfy existing pledges to the schools.

The supporters’ argument is falling short with a sizable number of people who, according to The Post poll, voted for slots in 2008 but plan to vote “no” this time. One is Doris Baumann, a retired fiscal manager from the Defense Department, who lives in Pasadena.

“I really don’t think the money is going to the schools. They can cook the numbers any way they want,” Baumann said. “I thought it would probably be good to have some gambling. Now, I think they have enough.”

I and many others had expected that gambling would cruise to approval this year, given that the referendum four years ago won by a 17-point margin. We hadn’t accounted for the difference that in 2008 there was plenty of heavy-duty casino money to back the proposal but no equivalent resources available to opponents.

“Four years ago, you had people who were opposed, but all of the effort, all of the money was on the ‘for’ side. This year, you have Penn National funding a very aggressive campaign against the vote, because they have a lot to lose at Charles Town,” said state Sen. Rich Madaleno (D-Montgomery), who supports Question 7.

His colleague, Sen. Brian Frosh (D-Montgomery), who opposes the measure, welcomed the change.

“For once, it’s a fair fight. Last time around, the churches and folks who were concerned about social illnesses and law enforcement couldn’t fund the opposition. Now there’s a billionaire, or several, on their side,” Frosh said.

I still hope the fair fight’s outcome is a new casino for Prince George’s. It needs jobs and development — which the county would get regardless of what happens with the state schools money. If that result also chagrins the charlatans at Penn National, then so much the better.

For previous Robert McCartney columns, go to washingtonpost.com/mccartney.