Rep. Mark Pocan (D-Wis.), a leading progressive in the House, disappointed some liberal activists by endorsing a left-leaning senator’s challenger this past week.

Pocan, co-chair of the Congressional Progressive Caucus, announced that he is backing Rep. Joe Kennedy III (D-Mass.), who is challenging veteran lawmaker Sen. Ed Markey (D-Mass.), the Senate’s leading champion of a Green New Deal.

Markey’s collaboration with Rep. Alexandria Ocasio-Cortez (D-N.Y.) on the original Green New Deal resolution has earned him the support of Ocasio-Cortez and left-leaning Rep. Ro Khanna (D-Calif.), as well as backing from Sunrise Movement, the youth-led climate group.

Kennedy’s bid to unseat Markey is the unusual contest where a somewhat more moderate Democrat is trying to unseat a progressive stalwart.

But on Tuesday, Pocan — along with former CPC co-chair Rep. Raúl Grijalva (D-Ariz.) and 16 other House Democrats — announced that they were endorsing Kennedy, shocking progressive activists in Markey’s corner.

“As a proud, progressive voice in Washington, Joe has been a tireless champion for social and economic justice,” Pocan said in a statement. “From fighting for mental health parity, to protecting the rights of transgender Americans and advocating for a more inclusive economy, Joe offers the moral clarity and energized leadership that our country and party need today more than ever before.”

In an accompanying statement, Grijalva focused on Kennedy’s ability to “build coalitions and unite his colleagues behind progressive causes.”

If the head of the Progressive Caucus is going to weigh in on primaries, our hope is that he would do it on the side of progressive champions. Waleed Shahid, Justice Democrats

NARAL Pro-Choice America and the influential local union 32BJ SEIU have endorsed Markey. But there are plenty of national groups that have yet to weigh in on the race one way or another, including MoveOn, Democracy for America, and Our Revolution.

A newer generation of left-leaning activists, many of whom have embraced an intersectional vision for tackling climate change, see Markey as the obvious choice.

“Progressives should endorse progressives,” said Julian NoiseCat, vice president of policy and strategy at the think tank Data for Progress. “It’s not complicated. If we want power we have to stick out for our own.”

“Markey going out and working with Ocasio-Cortez was an incredible act of leadership,” said Evan Weber, a political strategist at the Sunrise Movement. “If he doesn’t win his primary, the right-wing narrative will be that it’s because he supported the Green New Deal.”

He added that the move “undermines” Pocan’s own support of the Green New Deal.

In addition to climate change, Markey is a seasoned expert in telecommunications policy. He has become Senate Democrats’ top spokesman for reinstating net neutrality rules. Among other things, those rules — which the Trump administration discarded — forbid internet service providers from providing internet at different speeds based on what content creators pay them.

Activists have been closely watching where lawmakers are choosing to endorse challengers to incumbents in the 2020 election, encouraging sitting legislators to stand up for progressive allies and jump in where it can count. Sen. Bernie Sanders (I-Vt.) drew criticism in December for his refusal, thus far, to endorse immigration attorney Jessica Cisneros, a primary challenger in Texas backed by Sen. Elizabeth Warren (D-Mass.), Ocasio-Cortez and the left-wing Justice Democrats.

Tom Williams/CQ-Roll Call, Inc/Getty Images Rep. Mark Pocan (D-Wis.), a co-chair of the Congressional Progressive Caucus, argues that Rep. Joe Kennedy (D-Mass.) would raise the profile of liberal priorities in the Senate.

Waleed Shahid, a spokesman for Justice Democrats (which has not endorsed in the Massachusetts primary), said the Bay State race was not where he’d like to see top progressive members endorse someone against the incumbent.

“If the head of the progressive caucus is going to weigh in on primaries, our hope is that he would do it on the side of progressive champions,” he said.

Spokespeople for Reps. Ocasio-Cortez and Khanna, both of whom are members of the Congressional Progressive Caucus, declined requests to comment on the matter. A spokesperson for Grijalva did not respond to a request for comment.

In an interview with HuffPost, Pocan disputed the idea that Kennedy is a “centrist,” noting that Kennedy has a 97% score on the left-leaning congressional voting scorecard site Progressive Punch, while Markey’s is 99%. (Scorecards are inherently limited, and Progressive Punch gives Markey a higher rating than Sanders.)

Part of Kennedy’s appeal is his family pedigree (he is a grandson of New York Sen. Robert F. Kennedy and grand-nephew of former President John F. Kennedy), and the money and attention it can bring.

“When Joe Kennedy supports something it gets lots of attention because he’s Joe Kennedy ― far more than when Ed Markey gets his name behind something,” Pocan said, adding that Kennedy is also “a passionate speaker. He does a very good job of relating to the public.”

Alex Wong/Getty Images Sen. Ed Markey (D-Mass.) unveils the Green New Deal resolution alongside Rep. Alexandria Ocasio-Cortez (D-N.Y.) in Feb. 2019.

‘A Pretty Silly Debate’?

Kennedy’s defenders, including Pocan, insist that the differences between him and Markey on policy are minor to the point of being inconsequential.

“If people want to debate that you’re saying ‘six’ instead of ‘half a dozen,’ I think that’s a pretty silly debate,” Pocan said.

In fact, Kennedy, a member of the CPC, is a solid progressive by national standards. His campaign notes that he both rejected corporate PAC money and got behind marijuana legalization sooner than Markey.

Both Markey and Kennedy have endorsed Warren for president. And though Markey voted to authorize the Iraq War in 2002, he and Kennedy both voted against the bipartisan 2019 defense spending bill, which omitted legal restrictions on the Trump administration’s ability to escalate the crisis with Iran.

Broadly speaking, Kennedy is personally close to House Democratic leadership, a proximity evident in his selection to deliver the official response to President Donald Trump’s state of the union address in January 2018.

Markey, by contrast, has sought to more explicitly ally himself with the ascendant grassroots left. In speeches, he has begun cheekily arguing that if the oil and gas industry’s tax subsidies amount to “socialism,” then the U.S. should give renewable energy sources “some of that socialism.”

The two candidates’ divergent approaches to a race for district attorney in Suffolk County, Massachusetts, which includes Boston, are also revealing.

Markey declined to endorse a candidate in the primary. Kennedy did not formally endorse his friend Greg Henning, the centrist candidate, but campaigned with him the day before the primary vote.

Rachael Rollins, who defeated Henning and three others in the tight September 2018 race, is one of the most progressive prosecutors in the country. Rollins endorsed Markey’s reelection in October.

There is also apparent concern that an expensive Senate primary, which will last until September, will prevent progressives from devoting their resources to competitive state legislature primaries and hotly contested federal contests in neighboring Maine and New Hampshire.

Dia Dipasupil/Getty Images Rep. Joe Kennedy III (D-Mass.) is able to generate money and attention partly due to his pedigree. But Kennedy's boosters say he is a talented speaker and deal-maker as well.

“A lot of people in Massachusetts, even if they like primary challenges in general, are irritated with the idea of a very drawn out, expensive primary battle,” said Jonathan Cohn, chair of the elections committee of Progressive Massachusetts, a statewide left-wing group, which has yet to endorse in the Senate race.

The left’s most specific knock on Kennedy is likely his refusal to join the House’s single-payer health care bill until March 2019. Markey, who is a co-sponsor of Sanders’ Senate bill, has backed single-payer legislation since 2009, when he was in the House.

“I don’t know [Kennedy] as pushing the ball forward on issues and I know on something like single payer there was a lot of organizing that it took to get him to that position,” Cohn said. “The question for Massachusetts voters is: Who is it easier to push?”

When announcing his support for “Medicare for All” in February 2019, Kennedy maintained ― and Pocan affirmed to HuffPost ― that his objections to previous iterations of the bill were on progressive grounds. He was concerned that, prior to improvements in the new legislation, the bill did not cover long-term care and did not strike down the Hyde Amendment, which bars federal funds from being used to cover abortions.

“Joe is proud of his progressive record and deeply grateful for the support of leaders like Rep. Pocan and Rep. Grijalva,” said Kennedy campaign spokeswoman Emily Kaufman.

Kennedy has been endorsed by three local progressive elected officials: Boston City Councilor Matt O’Malley; Berkshire County District Attorney Andrea Harrington; and Brookline Select Board Member Raul Fernandez, who was endorsed by Ocasio-Cortez, a former college student of his.

Brian Snyder / Reuters Kennedy and Markey attend a speech by Sen. Elizabeth Warren (D-Mass.) in Boston on Dec. 31. Both men have endorsed her White House bid.

A ‘Strong Personal Relationship’

In his interview with HuffPost, Pocan also admitted that the endorsement is partly based on his “strong personal relationship” with Kennedy, who entered Congress in 2013, the same year Pocan did.

That some members of Congress prioritize personal relationships over policy and ideology is a sore point with progressives. For example, activists were dismayed when then-Rep. Beto O’Rourke decided not to endorse the Democrat who was challenging his friend, Rep. Will Hurd (R-Texas), in a close race.

“Pocan is choosing friendship over progressive alliances and it’s sad to see from the CPC head,” said an aide to a progressive House Democrat, who requested anonymity because they were not authorized to speak on the matter.

Then there’s the matter of Pocan endorsing Kennedy just two days before announcing his support Bernie Sanders’ presidential race, which struck even unaligned progressives as dissonant.

“Bernie and Kennedy is a weird pairing,” said a progressive strategist, who declined to be named because their organization has not endorsed in the race.

Pocan said he endorsed Kennedy months ago privately and the campaign chose to announce it when it did for its own reasons. He said he has no plans to campaign for Kennedy, but is due to hit the trail for Sanders.

Meanwhile, Pocan has not announced his support for any of the progressive primary challengers taking on conservative House incumbents. He backed nonprofit executive Marie Newman’s bid against abortion rights opponent Rep. Dan Lipinski (D-Ill.) in 2018, but has yet to weigh in on her rematch run this cycle. He has also stayed out of Cisneros’ race against Rep. Henry Cuellar (D-Texas), a longtime gun regulations opponent who approved of Trump’s assassination of Iranian General Qassem Soleimani.

The CPC’s political action committee is still discussing which candidates it will back before getting further involved in races. The Texas House primaries are on March 3, which is Super Tuesday ― a day when 40% of the Democratic presidential nomination delegates are in play.

Will Pocan eventually endorse Cisneros?

“I have no fucking idea. How’s that for an answer?” he replied. “I don’t know yet.”

CORRECTION: This story previously stated that Markey endorsed Rachael Rollins in her primary race for Suffolk County district attorney. He endorsed her in the general election.