"They were always such a loving and supportive couple and are incredibly close, especially for a couple in politics," one source tells PEOPLE about the Gores, who announced on Tuesday that they are separating.
"They were always affectionate and loving and a tight family unit," adds the source. "I am shocked."
While the couple and Gore's spokeswoman did not elaborate on details of the split, another friend says it's unlikely a third party was involved. "I believe completely this is not one of those [cheating] situations in any remote way," the pal tells PEOPLE.
And if the Gores were having problems, they kept it private, adds the first source.
"[Just last month] he was his usual self – polite, friendly, engaged," the source says. "There was not even a trace of anything being wrong. I can't tell you how shocking the news is."
Reporting by ELIZABETH LEONARD and SANDRA SOBIERJA WESTFALL