With primary voters in the home states of all of the presidential frontrunners set to go to the polls today, Primary Source thought it might be good to take one last look at the contenders’ Congressional support back home.

[IMGCAP(1)]What we found was this: Rep. Dan Lipinski (D-Ill.) appears to be the odd man out.

Lipinski and House Democratic Caucus Chairman Rahm Emanuel (Ill.) are the only Democrats in the Prairie State delegation who have not endorsed Sen. Barack Obama (Ill.).

Emanuel has a good enough excuse, having worked in the Clinton White House. But also being from Chicago, he has said he would remain neutral in the primary race between Obama and Sen. Hillary Rodham Clinton (N.Y.).

But we wondered, what was Lipinski’s reason?

Except for Obama, all of the remaining top-tier presidential contenders have the backing of their respective home-state delegations on Capitol Hill.

All of the New York Democrats in Congress are with Clinton, and all of the Republicans from Arizona are with Sen. John McCain (R-Ariz.). Even Rep. John Boozman, the lone Congressional Republican from Arkansas, is with former Arkansas Gov. Mike Huckabee (R). As for former Massachusetts Gov. Mitt Romney (R)? Well, there aren’t any Bay State Republicans in Congress.

Lipinski’s office was contacted for comment on why their boss is staying out of the presidential primary. As of late Monday afternoon, we received no response.

Lipinski has a primary of his own to contend with today, against former prosecutor Mark Pera (D), a darling of the net roots and ultra-liberal groups.

For the record, Pera hasn’t publicly indicated his presidential preference either.

— Lauren W. Whittington