Thomas Hale Boggs Jr., a son of congressional royalty who evolved into a top-tier lobbyist and prolific Democratic fundraiser and embodied what it meant to have Washington clout, died Monday. He was 73.

His brother-in-law, journalist Steve Roberts, said Boggs died Monday morning at his home in the Washington suburb of Chevy Chase, Maryland. The cause of death has not been determined, but the family suspected a heart attack, Roberts said.

Boggs was a driving force in transforming the law firm now known as Squire Patton Boggs into one of Washington's most influential and best-known lobbying powerhouses. A Washington lifer with an encyclopedic list of Democratic contacts, he was also known for constantly hosting fundraisers and relentlessly persuading friends and family to contribute to Democratic candidates.

It was that combination of making things happen inside the government and raising money for political insiders that over the decades propelled him to the upper ranks of the capital's power brokers.

Underscoring Boggs' stature -- particularly among his fellow Democrats -- Senate Majority Leader Harry Reid, D-Nev., opened Monday's session by paying him tribute, calling him "an institution in this city." Earlier Monday, House Minority Leader Nancy Pelosi, D-Calif., called the home of Boggs' sister, the journalist Cokie Roberts, to express her sympathies, said Steve Roberts, Cokie Roberts' husband.

Boggs was an active lobbyist and fundraiser until the end, having recently hosted such a gathering for Rep. Nita Lowey, D-N.Y., Cokie Roberts said. So far for this year, reports filed with the Senate indicate he was representing a half-dozen clients including Amazon.com and CITGO Petroleum Corp.

Tommy, as he was known, was the son of Thomas Hale Boggs, who was House majority leader, and Lindy Boggs, who succeeded her husband as a representative after his plane crashed during a campaign trip to Alaska in 1972. Between them, the two Democrats represented Louisiana in the House for nearly half a century combined.

Involved in Democratic politics from an early age, Boggs did advance work for President Lyndon Johnson's 1964 campaign, according to Steve and Cokie Roberts. He also worked as an economist for Congress' Joint Economic Committee, according to the Squire Patton Boggs website.

In 1966, Boggs joined the four-year-old firm that would later bear his name, which was headed by the attorney James R. Patton Jr. and focused at the time on international business. With Boggs aboard, the company evolved into one that lobbied broadly across the scope of government and on a range of issues. And Boggs' own influence began to grow.

So far this year, Squire Patton Boggs has reported $17.8 million in lobbying income, more than any other firm, according to the nonpartisan Center for Responsive Politics, which monitors lobbying. The firm says it now employs nearly 350 attorneys and other professionals in offices around the globe.

In 1970, Boggs tried entering the House on his own right, running for a seat in the capital's Maryland suburbs as a Democrat. He was defeated by Republican incumbent Rep. Gilbert Gude.

Boggs was close to his father and was well known among Democratic lawmakers. When his father died, Rep. Thomas P. "Tip" O'Neill Jr., the next ranking House Democrat, called other lawmakers seeking their support to succeed the senior Boggs as majority leader with the younger Boggs seated beside him, Steve Roberts said.

"He told them, `Tommy is at my elbow, I have his blessing,"' said Roberts.

As a lobbyist, Boggs helped engineer congressional approval of the 1979 federal bailout of the Chrysler Corp. and the 1993 North American Free Trade Agreement.