WASHINGTON -- The chairman of U.S. Sen. Robert Menendez's re-election campaign is a lobbyist whose clients include special interests that come before committees the senator sits on -- including foreign governments and a firm proposing a natural gas pipeline in New Jersey.

Records reviewed by NJ Advance Media show Mike Soliman's clients include the government of Qatar and New Jersey's largest health insurer, Horizon Blue Cross Blue Shield. Menendez is the top Democrat on the Senate Foreign Relations Committee and a member of the Senate Finance health subcommittee.

Soliman also lobbies for the Penn East Pipeline Co., a proposed 120-mile natural gas pipeline from the Marcellus Shale region of Pennsylvania to Mercer County, while Menendez sits on the Finance panel that tackles energy issues.

Soliman's dual roles of lobbyist and campaign executive break no laws and are not uncommon, though they do raise concerns among government watchdogs.

"It matters more than a $1,000 contribution to be a skilled campaign director," said Paul Seamus Ryan, vice president for policy and litigation for Common Cause. "It is really common and it's really problematic to have lobbyists become such crucial parts of an officeholder's campaign team."

Soliman, a partner in the lobbying firm Mercury Public Affairs, said he would refrain from lobbying Menendez while running the senator's re-election effort.

"The reason this information is public, as it should be, is because I have always been fully transparent, above board and properly disclosed; this is all part of the public record," Soliman said. "But out of an over-abundance of caution, I will not directly or indirectly lobby the senator or his staff on behalf of any client for the duration of the campaign."

Soliman's clients paid Mercury $460,000 during the first six months of the year, House lobbying records show. For Horizon, Soliman's disclosure form said his tasks included "lobbying NJ Congressional Delegates among others when needed."

"It's predictable that an elected officeholder would be grateful to his campaign staff that got him elected or re-elected," Ryan said. "When that campaign staffer is a lobbyist, it definitely creates a conflict of interest."

The same issue ensnared the 2008 presidential run of U.S. Sen. John McCain, R-Ariz., where several top aides worked as lobbyists for domestic companies or foreign governments until they were asked to leave their jobs or the campaign.

"We very often see people revolving in and out of campaign positions and into lobbying or government," said Sheila Krumholz, executive director of the Center for Responsive Politics, a Washington-based research group.

Including clients that Soliman does not lobby for, Mercury Public Affairs was paid $7.5 million in 2017 and $4.5 million during the first six months of 2018, according to the Center for Responsive Politics. The firm's other clients include Altria Group, the parent of Philip Morris; and the National Shooting Sports Foundation, a gun rights group.

Besides Qatar, Soliman lobbies on behalf of the government of Japan, according to the Center for Responsive Politics and the U.S. Justice Department. The Philadelphia Inquirer was the first to report that Soliman represents Qatar.

Soliman reached out to a Menendez aide earlier this year to arrange a meeting between the senator and the Qatari ambassador, according to a July Justice Department filing.

His tasks for Japan include "information gathering regarding local, state, and federal politics in New Jersey," according to a form filed in July with the Justice Department.

Mercury recently signed a contract to lobby for ZTE Corp., the Chinese telecommunications company that faced harsh penalties for doing business with Iran and North Korea in violation of U.S. sanctions until President Donald Trump intervened.

Referring to ZTE, Menendez said in May that Trump's business ties to China "raise the worrying possibility that he may be putting his own financial interests above the security and economic interests of the American people."

Separately, Mercury was paid $163,996 to lobby in Trenton last year, according to the New Jersey Election Law Enforcement Commission. Soliman's clients there also include PennEast.

Soliman's representation of PennEast is troublesome, said Jeff Tittel, director of the New Jersey Sierra Club, which opposes the pipeline. He said that while Menendez had a strong record on environmental issues, Soliman's campaign position could provide added heft in lobbying state officials.

Mercury's representation of foreign countries drew criticism from the Senate campaign of former Celgene Corp. executive Bob Hugin, Menendez's Republican opponent this fall.

"It should surprise no one that Senator Menendez and his top adviser have a massive blind spot when it comes to unethical behavior and conflicts of interest," Hugin campaign spokeswoman Megan Piwowar said.

"The fact that Senator Menendez's campaign chairman is paid a ton of money to lobby on behalf of foreign governments that come before the senator's committee is completely unacceptable," she said.

Menendez campaign spokesman Steven Sandberg said Hugin had some lobbying issues to address as well.

Celgene last year under Hugin spent $2.8 million -- its highest total ever, according to the Center for Responsive Politics -- as it helped block legislation designed to make it easier for generic companies to produce less-expensive versions of its Revlimid cancer drug.

"Hugin's multimillion-dollar lobbying effort put tens of millions in Hugin's pocket at the expense of cancer patients who had no choice but to purchase his medication," Sandberg said.

Jonathan D. Salant may be reached at jsalant@njadvancemedia.com. Follow him on Twitter @JDSalant or on Facebook. Find NJ.com Politics on Facebook