Voters in Maryland's 6th Congressional District have been hearing a familiar Arkansas drawl on the phone this week: It's Bill Clinton calling, letting them know he thinks the world of Democratic candidate John Delaney.

All over the state, Marylanders have been receiving robocalls from celebrities and elected officials delivering messages for or against state ballot issues or political candidates. The voices of "Desperate Housewives" actress Eva Longoria and magician David Copperfield tout the advantages of expanded gambling. State Del. Jill Carter recorded a call opposing that measure.

Voters often complain about the annoyance of receiving such calls or finding them on voice mail. But some political professionals say campaigns use them for a simple reason: They work.

Dale Emmons, a Democratic political consultant in Richmond, Ky., said robocalls work especially well when the voice on the recording is Clinton's.

"The fact that Bill Clinton would be willing to do that for a candidate is a significant decision because that's not something he does on a retail basis," said Emmons, president of the bipartisan American Association of Political Consultants.

In his call for Delaney, Clinton tells voters that the challenger to Republican Rep. Roscoe G. Bartlett is the son of a union electrician who has built his own successful business.

"You can count on John Delaney to stand up for the middle class and for our Democratic values," Clinton says. The Bartlett campaign did not respond to a request for comment.

In academia, there are skeptics who believe robocalls are a pitifully ineffective campaign tool. "You might as well take this money out of your budget and light it on fire. That's how effective these robocalls are," said Michael Miller, political science professor at the University of Illinois at Springfield.

Miller said the main attraction of the technique is its low cost.

"It's relatively cheap. It's cheaper than mail. It's cheaper than getting somebody to make the calls for you, but you get what you pay for," he said. "People are sophisticated enough to know what it is and hang up immediately."

Todd Eberly, who teaches political science at St. Mary's College of Maryland, shares Miller's disdain — even when a former president is involved. He said the only benefit for a campaign is the attention the calls garner from the news media when a celebrity is involved.

"There's absolutely no indication that robocalls accomplish anything," he said. "People are not going to say, 'Wow, the disembodied voice of Bill Clinton! Let me sit here and listen.' "

But Justin Schall, Delaney's campaign manager, said that during 18 years of running election operations, he's learned differently.

"Like most things in life, it's not black and white. It's how you use the robocall," he said. "We did this with Bill Clinton in the primary and it was incredibly effective."

Clearly, many political professionals running campaigns in Maryland this year agree that robocalls have their place in a modern campaign. Both the state Democratic and Republican parties say they use robocalls for specific purposes and find them effective.

Matt Verghese, spokesman for the Maryland Democrats, said the party uses robocalls primarily for get-out-the-vote efforts and for spreading news such as Gov. Martin O'Malley's decision to extend early voting hours after superstorm Sandy.

Verghese said the party typically uses recorded messages by elected officials including the governor and party executives. He acknowledged that sometimes the calls aren't well received.

"In campaigning, you hear complaints about everything," he said. "What you find out is, it works."

David Ferguson, executive director of the state GOP, said the Republicans also use robocalls for early voting drives and Election Day get-out-the-vote. But he said one of the most successful uses of the technique came in gathering signatures for the petitions to put measures such as the Dream Act and the new congressional map onto the Nov. 6 ballot in hopes voters will overturn them.

"Robocalls were instrumental in putting our petition efforts over the top," he said.