One of former Maryland governor Robert L. Ehrlich Jr.’s most trusted aides and a campaign consultant were accused Thursday of orchestrating tens of thousands of anonymous election-night robo-calls last year that prosecutors said were part of a larger attempt to suppress the black vote.

Paul E. Schurick, 54, Ehrlich’s de facto campaign manager, and Julius Henson, 62, a paid consultant, were indicted on multiple counts of election law violations stemming from an automated call that was placed to more than 110,000 Democrats in Baltimore and Prince George’s County, according to prosecutors.

With the polls still open, an unidentified woman’s voice told voters who answered to “relax” because Gov. Martin O’Malley (D) had already been “successful” in his rematch against Ehrlich.

There has been no indication that Ehrlich is a target of the probe by the Office of the Maryland State Prosecutor, which sought the indictments from a grand jury in Baltimore and which said its investigation continues.

But the episode could still stain the tenure of Maryland’s only Republican governor in a generation and further complicate efforts of Republicans to win statewide races in Maryland, where blacks account for a larger percentage of the population than anywhere outside the Deep South.

Paul Schurick, 54, was Ehrlich’s de facto campaign manager.

Based on documents obtained in the investigation, the indictments describe what prosecutors say was a strategy informed by Schurick and carried out by Henson to tamp down the black vote in hundreds of precincts.

The plan, according to the indictments, “centered on what was termed ‘The Schurick Doctrine,’ which was designed to promote confusion, emotionalism, and frustration among African American Democrats. . . . The plan stated that [t]he first and most desired outcome [of the Schurick Doctrine strategy] is voter suppression.”

Henson, a consultant who has primarily advised Democrats in mostly African American jurisdictions, took responsibility for the calls in November, saying the message was “counterintuitive” — that the calls were intended to motivate Ehrlich supporters to vote.

But investigators continued to look into the robo-calls, and Ehrlich was recently called to testify before a grand jury, according to the people familiar with the proceedings. Ehrlich, who did not return a phone call placed to his law office in Washington, has previously told reporters that he was unaware of the robo-calls and does not think that they are effective as a general strategy.

Ehrlich’s statement

In a statement issued Thursday afternoon, Ehrlich said: “I believe in the rule of law. I believe in my friend and colleague, Paul Schurick. I hope a fair resolution is reached as quickly as possible for both Paul and Mr. Henson.”

After losing to O’Malley by more than 14 percentage points last year, Ehrlich said he had no plans to seek elected office in Maryland again.

In seeking charges against Schurick, investigators reached into Ehrlich’s inner circle. Peter R. Zeidenberg, a Washington-based attorney for Schurick, said in a statement that the charges were based upon “a fundamental misunderstanding of the facts” and that Schurick would “vigorously contest” them.

Another member of Schurick’s defense team, Billy Murphy, who is black and is based in Baltimore, said in a statement that he had known Schurick for decades and that he would “never do any of these things.”

Neither Henson nor an attorney representing him returned phone calls Thursday.

The indictments might be the first in the country involving Election Day attempts to suppress voting using robo-calls, experts said. The case also appears to be a rarity nationwide, one in which prosecutors might have the physical evidence necessary to prove intent to commit voter suppression, experts said.

“I have taught elections law for decades, and never in my life have I seen anything like this,” said Larry S. Gibson, a professor at the University of Maryland Law School. “It’s the unusual case of having a smoking gun. Usually intent has to be implied by a person’s conduct. . . . Here, it is in writing.”

Gilda Daniels, an elections law expert at the University of Baltimore Law School, said the records of the calls could provide unusually firm evidence.

“There is a long history in urban areas of people passing out fliers that say Republicans vote on Tuesday and Democrats vote on Wednesday, and specifically in Maryland of ploys telling people if you owe tickets or back child support that you can’t vote,” Daniels said. “But this isn’t someone printing off fliers that can’t be easily tracked. These are phone calls, and there are records of them.”

In a filing in a separate civil case stemming from the episode, Henson’s attorney, Edward Smith Jr., argued that even political “dirty tricks” are protected free speech.

The indictments brought Thursday charge both Schurick and Henson with three counts of conspiracy to violate election laws, one count of influencing votes through fraud and one count of failing to identify the sponsor of the calls. In addition, Schurick was charged on one count of obstruction of justice.

All but one of the charges handed down Thursday carry maximum prison sentences of five years.

The indictments allege that an employee of Henson’s firm forwarded test calls of the misleading robo-call to the cellphones of Schurick and another top campaign aide before they were played more broadly. Henson also sent Schurick a text message alerting him to the cost of the calls, according to the indictments.

The indictment alleges that call lists used by Henson’s firm on Ehrlich’s behalf came from two previous clients — both Democrats whom Henson tried to help win September primaries: Marilynn Bland, a successful candidate for Circuit Court clerk in Prince George’s County, and Deborah Claridy, a candidate for sheriff of Baltimore.

Black voter turnout

The African American vote was expected to break heavily for O’Malley, a former mayor of Baltimore. During the campaign, aides to Ehrlich spoke freely about how black turnout could affect his election prospects.

In 1994, a strong Republican year in the state, black voters accounted for only 12 percent of the electorate. During the subsequent three cycles, African Americans made up between 21 percent and 23 percent of the electorate.

According to Thursday’s indictments, the full recording stated: “Hello. I’m calling to let everyone know that Governor O’Malley and President Obama have been successful. Our goals have been met. The polls were correct, and we took it back. We’re okay. Relax. Everything’s fine. The only thing left is to watch it on TV tonight. Congratulations, and thank you.”

Earlier in his career, Schurick worked for one of Maryland’s most prominent Democrats, the late former governor William Donald Schaefer. Schurick joined Ehrlich’s congressional office in 1997 and became a member of his inner circle, serving as his communications director during Ehrlich’s four-year tenure as governor, which ended after his 2006 defeat by O’Malley.

Several Ehrlich associates have said that they think it is plausible he knew nothing about the calls.

“Governor Ehrlich is the kind of person who trusts people around him to do their jobs,” said Richard Cross, a former Ehrlich aide who played no role in the 2010 campaign.

State Prosecutor Emmet C. Davitt, whose office brought the charges against Schurick and Henson, was appointed in November by O’Malley to a six-year term. The jurisdiction of the office, which operates independently of the governor, includes election law cases. The robo-calls episode is also the subject of a separate civil suit brought by Attorney General Douglas F. Gansler (D) in federal court.

Staff writers Aaron C. Davis and Miranda S. Spivack contributed to this report.