Stop by the office of almost any Maryland lawmaker this week, and you’ll probably find the lights off and nobody home. Leave a message for any lobbyist registered in the state, but don’t expect a reply anytime soon.

But if your job is running Maryland government — or trying to influence it — you’ll be in Ocean City, along with about 2,000 other elected leaders, lobbyists and corporate sponsors for four days of sand, seafood, sunrise yoga and meetings sprinkled in between.

The gathering’s annual crab fest and long nights at beach-side bars with lobbyists picking up the tabs are derided perennially for the way they let special interests pay to cozy up to Maryland’s elected leaders.

Arguably, however, the most powerful lobbyist again this year won’t be anyone forced to wear a badge saying so, but the group of county officials that puts on the state’s summertime political juggernaut.

The Maryland Association of Counties, or MACo, as it’s known in state power circles, holds one of the best track records in Annapolis for killing proposals it dislikes and greasing the wheels to pass legislation it wants. And the group’s not-to-be-missed August gathering doubles as its not-so-subtle launch for a yearly blitzkrieg of lobbying.

The organization focuses almost exclusively on one goal: keeping money and power flowing from the state to monied and powerful Maryland counties.

And with Gov. Martin O’Malley (D) again tiptoeing toward recommending cuts to the group’s coveted sources of revenue and influence, the focus of MACo — pronounced “may-co” — is again laser-like as lawmakers head to the beach.

“Maryland counties are some of the most powerful nationwide. They have single-handedly killed legislation that some people think would have benefited the state,” said Donald F. Norris, chairman of the public policy department at the University of Maryland Baltimore County.

With a membership that includes all 23 Maryland counties and Baltimore, MACo derives part of its power from having state lawmakers from its liberal urban areas and rural conservative ones seek to do its bidding in Annapolis. Part of the group’s largess also comes from the size of some counties. Montgomery alone has a budget larger than those of almost a dozen U.S. states.

“They’re big, and this year they will have another fight: O’Malley is trying to get the camel’s nose a little further into the tent,” Norris said. “But it won’t be easy. Power in Maryland tips very, very much in favor of MACo.”

Thanks to decades of effective lobbying, MACo is largely the reason counties set teachers’ pay even as the state is responsible for paying most rising pension costs, calculated on high salaries it doesn’t control. It’s why Maryland counties are among the only ones in the country with the power to set their own income tax and leave the mess of collecting the money to the state. And it’s why, despite decades of attempts by Maryland governors to pass statewide guidelines for smart growth, counties have kept the state’s hands off lucrative development and land-use decisions, which has also led to corruption in some counties.

“My county is [damaged] permanently because of . . . poor development decisions by the County Council,” said state Senate President Thomas V. Mike Miller Jr. (D), referring to a swath of his district in Prince George’s County, where former county executive Jack B. Johnson (D) is awaiting sentencing after pleading guilty to taking more than $400,000 in developer bribes. “Southern Prince George’s has got some very terrible decisions by people paid off by developers. . . . Counties can’t have the control.”

“Don’t get me wrong,” continued Miller, who has come to scorn the annual Ocean City retreat. “I think counties are an important constituency. . . . But it’s sheer insanity that the state has given the counties a share of our income tax. That’s the reason people say we’re a tax hell, because our counties have an income tax, and they pile it on top of our state income tax.”

Howard County Executive Ken Ulman, this year’s MACo president, has a different take. “The legislature and governor, currently and historically, have understood that most basic government services are delivered through local government, so we have to have a critical partnership and the funding needed to do that. . . . Not everyone in Annapolis shares that appreciation, so that’s why we have a strong organization that does a lot of education.”

A lot of that euphemistic teaching begins each year at Ocean City. “Anybody who thinks it is people lounging on the beach all day, come with me,” Ulman said. “I won’t have a moment to breathe between meetings.”

As in years past, many of MACo’s most important moments will take place behind closed doors at the Roland E. Powell Convention Center. Like governors before him, O’Malley is again scheduled to give MACo’s board of directors a private preview of his budget plans.

Two years ago, aides said, that discussion helped push O’Malley to close a state budget gap by cutting highway maintenance funds for counties. MACo leaders have complained publicly about the cuts but at the beach meeting stressed privately that they would rather go with that option than have O’Malley shift pension costs to counties, which MACo members viewed as tougher to reverse when the economy improves, said several who were at the meeting.

But O’Malley — a MACo member while mayor of Baltimore — has signaled that this year he may have no choice but to consider shifting a greater share of teacher pension costs to counties to close another shortfall, estimated at more than $1 billion.

Unlike private maneuvering over the budget, however, another source of long-standing tension between MACo and the state will come into full view this year at the meeting.

O’Malley plans to moderate a public forum on his administration’s Plan Maryland, a statewide effort to tie together Maryland’s patchwork of smart-growth strategies.

It’ll be a Democratic governor’s latest attempt to go where many have failed before.

Since the 1970s, MACo has successfully killed legislation backed by Democratic governors Marvin Mandel, William Donald Schaefer and Parris N. Glendening to impose tougher guidelines against sprawl.

More often than not, the governors’ efforts have ended with legislation that went the other way, codifying local power over development authority.

And in between those attempts, when the state seeks to tighten environmental regulations, the issue often comes to a head again because limits on such matters as storm-water runoff and new septic systems can impinge on local development autonomy.

MACo’s opposition is often so predictable that Del. Maggie L. McIntosh (D-Baltimore), chairwoman of the House environmental committee, has at times in hearings taken to introducing the group’s associate director, Leslie Knapp, as “Dr. No.”

“ ‘Dr. No,’ yes, it is a term of endearment; he is a loving human being,” McIntosh said, “I use it because sometimes I have to make light of the situation . . . when it comes to zoning, growth issues, environmental issues, they are very much in the driver’s seat in many ways.”

For his part, Knapp has quipped back in hearings that he’s “Dr. K-n-o-w,” knowing what’s best for counties and state policy. The General Assembly has often agreed. MACo had a success rate on legislation last year of 78 percent, which has been roughly consistent for the past two decades.

“We represent not a single particular interest, but all counties,” Knapp said. “We have urban, we have rural, and we have to synthesize and recognize the issues those counties care about most.”

O’Malley has tapped Richard E. Hall, his secretary of planning, who has spent decades in the agency learning from the state’s dealings with MACo, to try to massage Plan Maryland into something counties could support. Still, he said he expects a “forceful” discussion at the beach.

Montgomery County Executive Isiah Leggett (D) promised it would be that. “Land use is a local matter, and any attempt to usurp that we would, MACo would, fight against,” Leggett said. To those who might say MACo and counties have too much power: “I would disagree. To the extent there is power, we may not have enough.”