US congressman Joe Kennedy III has announced he is running for the senate.

The Massachusetts Democrat – a grandson of Robert F Kennedy – formally announced his campaign on Saturday in an email before a launch event in East Boston.

This is where the Kennedy clan first settled after arriving from Ireland well over a century ago.

Joe Kennedy
Mr Kennedy is the grandson of Robert F Kennedy (AP)

He is the first member of America’s most famous political dynasty to run for the senate since his great-uncle Edward M Kennedy did so in 1962, a year before his great-uncle John F Kennedy’s assassination.

The 38-year-old will face 73-year-old incumbent senator Edward Markey in next year’s primary.

He told supporters: “I’m running because our country is at a moment of truth.

“Donald Trump has forced a long overdue reckoning in America. And how we respond will say everything about who we are.”

Joe Kennedy’s father, Joseph Kennedy, also served in congress. Others elected to office include former US representative Patrick Kennedy II and Kathleen Kennedy Townsend, who served two terms as Maryland’s lieutenant governor.

First elected to congress in 2012, Mr Kennedy has tried to position himself as more of a pragmatist than those on the left of his party.

Nevertheless, he has adopted many of the causes driving the party’s liberal wing.

He has called for congress to initiate impeachment efforts against President Donald Trump and has backed a “Medicare for All” bill in the House of Representatives.

Mr Kennedy has also said he supports the Green New Deal initiative to combat climate change, something Mr Markey is championing along with Democratic representative Alexandria Ocasio-Cortez of New York.

Given his political pedigree, Mr Kennedy has been seen as a rising star in the party.

In 2018, he was tapped to deliver the Democratic response to Mr Trump’s State of the Union address.

A Kennedy-Markey contest will put more than a few high-profile Democrats in an awkward position, most notably senator Elizabeth Warren, the White House hopeful from Massachusetts.

Ms Warren has worked with Mr Markey in the senate and taught Kennedy at Harvard Law School. She formally endorsed Mr Markey before Mr Kennedy floated the idea of a challenge.

Mr Markey, who joined thousands of young climate change activists who rallied in Boston on Friday as part of a global, youth-led day of environmental action, has the backing of many environmental activists.

One of those groups – Environment Massachusetts – has vowed to raise five million dollars (£3.98 million) to help Mr Markey win re-election.

Mr Markey already faces two lesser-known candidates: Shannon Liss-Riordan, a workers’ rights lawyer, and Steve Pemberton, a former senior executive at Walgreens.