The officials spoke on the condition of anonymity to freely describe the plans.

Kennedy met with Markey on Wednesday to tell him in person, a source said.

The matchup between the men will mirror some of the generational tensions emerging in the 2020 presidential primary, in which younger candidates have argued that it’s time for a new generation of leaders. While Kennedy, a 38-year-old millennial, and Markey, a 73-year-old baby boomer, do not diverge much on core Democratic issues, they present a distinct choice to voters about what they want the future of the party to look like.

Yet, unlike insurgent primary challenges from the fringes of the party, both Kennedy and Markey have deep ties to Massachusetts Democratic politics, and a competition between them could be unsettling for donors in the state who have long supported both men.

Kennedy, grandson of the late attorney general and New York senator Robert F. Kennedy, has only been in Congress since 2013, but his family’s political legacy in the state dates to the late 1800s.

Markey has been in Congress since 1976, first in the U.S. House and then in the Senate, after winning a special election in 2013. Markey has already received the endorsement of fellow Massachusetts Sen. Elizabeth Warren, a top-polling candidate for president, and Rep. Alexandria Ocasio-Cortez, D-N.Y., the 29-year-old freshman and liberal star.

Ocasio-Cortez credited Markey, who had already served in Congress nearly 13 years when she was born in 1989, with being a “proud and strong progressive champion for working families” and with leading the push in the Senate for Green New Deal climate legislation: “Ed Markey was one of the few people that had the courage to stand up and take a chance,” she said.

Since Kennedy raised the specter of a primary challenge, Markey has sought to burnish his appeal – particularly to liberal voters – by highlighting his long record on climate change and other environmental issues.

“Elections are about choices, and Ed looks forward to spending the next 14 months campaigning hard every day to show the people of the Commonwealth why he’s the right choice. From lowering drug prices for our seniors, to expanding opioid treatment and recovery services, to creating green jobs for our workers, Ed Markey is ready to continue the fight for Massachusetts,” said Markey’s senior campaign adviser, John Walsh, in a statement.

Early polling in the state found Kennedy with an immediate edge over Markey, leading the veteran politician by 14 points in a head-to-head race, according to a Suffolk University/Boston Globe poll released earlier this month.

Kennedy is buoyed by his famous last name, but he’s also been held up as a rising star in the party, having been picked to deliver the Democrats’ official response to President Trump’s State of the Union address in 2018.

He is currently the only Kennedy family member serving in Congress. If elected to the Senate, he’d follow in the footsteps of not only his grandfather, but also more directly his two great-uncles who were both U.S. senators from Massachusetts, former President John F. Kennedy and former Sen. Edward M. Kennedy.