Here’s a list of the Senators and Governors that have not yet endorsed either Clinton or Obama, and my best guess for why they’re holding out.
Senators
Ken Salazar (CO)– although he prefers Clinton’s DLC style of politics, Obama won Colorado in a landslide and is ahead of McCain in the polls (while Clinton is not).
Joe Biden (DE)– I think he’s loyal to the Clintons to some degree, but I also think he fancies himself a statesman.
Tom Carper (DE)– this is the most surprising non-endorsement in the bunch. Carper is the prototypical DLC-style Clintonite politician. But Obama did win Delaware.
Tom Harkin (IA)– Harkin has hinted that he supports Obama and resents the way the Clintons have undermined the legitimacy of caucuses, but he might just feel some loyalty to the Clintons.
Mary Landrieu (LA)– Landrieu is the only Democratic senator with a competitive reelection contest this year. She can’t afford to alienate a big chunk of her supporters. In another year, she probably would have endorsed Clinton long ago.
Ben Cardin (MD)– Maybe he has a close relationship with the Clintons from his time in the House? Obama won his state in a landslide.
Carl Levin (MI)– He doesn’t want alienate either camp as he struggles to get Michigan’s delegates seated at the convention.
Max Baucus (MT)– He’s a DLC Democrat and his state hasn’t voted yet.
Jon Tester (MT)– His state hasn’t voted yet and he won this seat in a nail-biter. He can’t afford to piss off Clinton’s supporters.
Harry Reid (NV)– As Majority Leader, he is staying officially neutral.
Frank Lautenberg (NJ)– His non-endorsement is a de facto endorsement of Obama. He’s also facing a primary challenge from Rep. Rob Andrews and doesn’t want to alienate Clinton supporters.
Sherrod Brown (OH)– His state voted heavily for Clinton. Brown is a progressive and criticizes the DLC often.
Ron Wyden (OR)– I have absolutely no idea.
Jack Reed (RI)– Clinton won Rhode Island by a good margin.
Jim Webb (VA)– Won this seat in a real nail-biter and he can’t afford to alienate Clinton’s supporters.
Herb Kohl (WI)– When has Kohl expressed a strong preference for anything? I think he is friends with the Clintons.
Governors
Bill Ritter (CO)– He’s a real Clintonite centrist, but his state voted for Obama. He’s also hosting the convention and wants to maintain his neutrality.
Steve Beshear (KY)– State went hugely for Clinton.
Brian Schweitzer (MT)– State has not yet voted.
John Lynch (NH)– Clintons won the state and have cultivated the Granite State establishment for two decades.
Phil Bredeson (TN)– State went heavily for Clinton.
Joe Manchin (WV)– State went overwhelmingly for Clinton.
As you can see, most of these undecideds come from states that Clinton won but they have not endorsed her. The remainder are, for the most part, politicians that are politically vulnerable. The Montana pols are just waiting for their state to vote. I won’t do a rundown of the undecided House members but they basically fall into the same categories. They either come from districts that voted heavily for Clinton or they are too vulnerable to risk an endorsement.