FILE - In this June 26, 2018 file photo, Rep. Joe Kennedy, D-Mass., speaks during the "We Will Not Be Banned" protest sponsored by Muslim Advocates in front of the Supreme Court in Washington. In a Facebook post on Monday, Aug. 26, 2019, Kennedy said he's weighing a challenge to veteran Massachusetts U.S. Sen. Edward Markey in the 2020 Democratic primary. (AP Photo/Carolyn Kaster, File)

FILE - In this June 26, 2018 file photo, Rep. Joe Kennedy, D-Mass., speaks during the "We Will Not Be Banned" protest sponsored by Muslim Advocates in front of the Supreme Court in Washington. In a Facebook post on Monday, Aug. 26, 2019, Kennedy said he's weighing a challenge to veteran Massachusetts U.S. Sen. Edward Markey in the 2020 Democratic primary. (AP Photo/Carolyn Kaster, File)

BOSTON (AP) — Massachusetts Rep. Joe Kennedy III, a scion of one of America’s most storied political families, is taking steps to challenge Sen. Edward Markey in the 2020 Democratic primary, setting the stage for what could be a bitter intraparty battle split along generational lines.

It’s rare for challengers to take on incumbent senators, and such a move would be provocative at a time when Democrats are trying to wrest control of the Senate from Republicans. The potential matchup is notable because there doesn’t appear to be a deep ideological divide between the two lawmakers. But this is a time of churn in the Democratic Party, with a younger generation asserting itself, as seen in the presidential contest and in the House, where Rep. Alexandria Ocasio-Cortez of New York overtook a seasoned party leader in a primary race last year.

Kennedy, 38, filed a statement of candidacy with the Federal Election Commission on Monday, though in a Facebook post he stopped short of formally declaring a run against the 73-year-old Markey, who is seeking a second full term in the Senate after spending decades representing the state in Congress.

ADVERTISEMENT

“I am humbled by the words and actions of so many people supporting my potential candidacy. It means the world,” said Kennedy, a grandson of Robert F. Kennedy. “I plan to spend the next couple weeks talking to as many of you as I can, trying to figure out if this campaign is right for me and right for Massachusetts.”

Kennedy, who is in his fourth term in Congress, added that while some people have told him he should wait his turn, “I’m not sure this is a moment for waiting.”

The potential for what would be a serious, costly challenge to an incumbent delivered a jolt felt beyond Massachusetts. One national Democratic strategist said Kennedy’s potential candidacy was not helpful and was a waste of time and resources when Democrats would rather focus on loosening Republicans’ grip in battleground states to flip Senate control. The strategist was unauthorized to discuss the situation and spoke on condition of anonymity.

In recent weeks, speculation about a possible primary challenge of Markey has ramped up considerably.

At an event Monday in Boston, Markey said he’s “running hard on the issues the people of Massachusetts care most about,” citing the immigration and environmental causes and stricter gun laws he’s long championed. “That’s all I’ve done, from the day I was given the honor to represent this state, and that’s what I’m going to continue to do.”

When asked if he would still run even if Kennedy officially entered the race, he replied without uttering the name of his potential Democratic rival: “I am going to crisscross this state and I am going to give it everything I got.”

Kennedy is a rising star in the party who delivered Democrats’ rebuttal last year to President Donald Trump’s State of the Union address. He had previously signaled his intention to run for reelection in his House district, which stretches from the western suburbs of Boston to southeastern Massachusetts. He is seen as a valued member of the House, but with his sights set beyond his seat.

Toppling Markey, though, would likely become a race of style rather than substance. The senator draws widespread support from liberal and environmental groups, including the Sunrise Movement — the chief backers of the Green New Deal, the sweeping blueprint to transform the U.S. economy through combating climate change that he crafted with Ocasio-Cortez.

Markey will also have the support of the Democratic Senate Campaign Committee. The party’s campaign arm typically stands with incumbent senators, and that includes Markey, according to a committee official unauthorized to address the situation who spoke on condition of anonymity. Senate Majority PAC, an outside group aligned with Senate Democrats, is also seen as backing incumbents.

Much of the Massachusetts congressional delegation has also lined up behind Markey, with the notable exception of new Democratic Rep. Ayanna Pressley, a freshman ally of Ocasio-Cortez’s.

Massachusetts Sen. Elizabeth Warren, one of the party’s leading presidential candidates, endorsed Markey in a video last week.

“We need Ed Markey in the Senate now more than ever. And here’s why. Because he’s a leader. He’s a fighter. And he is a true progressive,” Warren said in a video offering her endorsement. “Ed is my friend and my partner in the Senate. I’ve got his back, and I know that he will always have yours. Let’s get Ed Markey reelected to the Senate.”

Kennedy’s father, Joseph P. Kennedy II, served in the U.S. House, as did his cousin, Patrick Kennedy of Rhode Island. His two great-uncles, former President John F. Kennedy and Edward M. Kennedy, also served in the U.S. Senate representing Massachusetts.

At the end of the last fundraising period, Joe Kennedy reported having $4.2 million cash on hand in his campaign account, barely edging Markey, who posted just over $4 million, campaign finance records show.

Two lesser-known Democrats, workers’ rights lawyer Shannon Liss-Riordan and businessman and author Steve Pemberton, previously announced their intention to run against Markey in the September 2020 primary.

___

Slodysko reported from Washington. Associated Press writers Philip Marcelo in Boston and Lisa Mascaro in Washington contributed to this report.