Call it loyalty or call it payback: The 2008 Democratic presidential primary lives on in Bill Clinton’s 2012 endorsements.

Former President Bill Clinton speaks at a 100th anniversary program for Arkansas Children's Hospital in Little Rock, Ark., Monday, March 5, 2012. (AP Photo/Danny Johnston)

Clinton has now endorsed in at least six Democratic primaries this year, according to our count. In all six of them, the candidate he’s backing supported or was tied to his wife, Hillary Clinton, in the Democratic primary four years ago, and their opponents supported President Obama in that race.

Allies of Clinton note that he makes no apologies about being loyal to those who have been loyal to him and his family. And, they add, he is the only member of the Clinton family free to dabble in politics — his wife is Secretary of State while his daughter works for NBC — which keeps him very busy in the endorsement game.

Drawing any conclusions beyond that — particularly regarding any sort of payback — is absolutely misguided, they argue.

Still, it’s an interesting trend. A quick rundown of where Clinton has chosen to play in the primary season is below.

* Clinton has endorsed Rep. Mark Critz (D-Pa.) over Rep. Jason Altmire (D-Pa.) in their primary Tuesday. Critz’s old boss, the late Rep. John Murtha (D-Pa.), was a key Hillary supporter in the House. Altmire, despite his district going heavily for Hillary, dithered on an endorsement and eventually backed Obama at the conclusion of the primary season — but before Hillary conceded.

* Bill Clinton has endorsed Pennsylvania attorney general candidate Kathleen Kane, who worked on Hillary’s campaign, over former congressman Patrick Murphy, who endorsed Obama.*

* Clinton’s backing Hillary-supporting Rep. Brad Sherman (D-Calif.) over Obama-supporting Rep. Howard Berman (D-Calif.) in a very contentious Member vs Member scrap.

* In a New Mexico congressional race, the former president is backing Hillary-supporting former Albuquerque mayor Marty Chavez over Obama-supporting state Sen. Eric Griego.

* Clinton is backing Hillary-supporting Rep. Silvestre Reyes (D-Texas) over competitive primary challenger Beto O’Rourke, who contributed $1,600 to Obama during the 2008 primary campaign.

* He supported Hillary fundraiser John Delaney in a Maryland congressional primary that Delaney won earlier this month over Obama-supporting state Sen. Rob Garagiola.

Clinton isn’t simply backing people who backed his wife in 2008; he’s also endorsing — whether coincidentally or purposefully — against people who supported Obama.

It’s not clear that he’s deliberately focusing on races that pit Hillary supporters against Obama supporters — rather than simply supporting people who supported his wife, regardless of who they face — but the result is the same: Obama’s 2008 supporters are running up against the Clinton family in the 2012 primaries. And Bill Clinton’s endorsement still carries plenty of weight in the Democratic Party.

Pennsylvania will be a good test of just how powerful Clinton is. Critz and Kane were both underdogs in early polls of their races, but Pennsylvania is very much Clinton country, so the endorsement could be a boost. (Clinton played a big role for candidates like then-Sen. Blanche Lincoln (D-Ark.) and Sen. Michael Bennet’s (D-Colo.) primary challenger, Andrew Romanoff, in 2010.)

Clinton spokesman Matt McKenna declined to comment on the former president’s endorsement formula.

Correction: This post initially said that Clinton endorsed Rep. Janice Hahn (D-Calif.) in her primary with Rep. Laura Richardson (D-Calif.). Clinton actually endorsed Hahn in his 2011 special election win. I regret the error.