Does the AP even bother with fact checkers?  I'm beginning to doubt it.
 
In this story, the AP relates the claims of the "town historian" of Derry, New Hampshire, who has connected John Kerry to the old sod. 

Derry town historian Richard Holmes said he's traced Kerry's lineage to an Irish immigrant believed to have introduced the potato to America.

Numerous publications have stated over the years that Kerry is Irish-American, which could help in Massachusetts, the most Irish state in the nation. Kerry said he's always corrected the misstatements.

....

James McGregor led a group of settlers from to New Hampshire in the early 1700s in search of political, economic, cultural and religious freedom. In 1720, according to local history, McGregor also planted the first potatoes in North America.

Now I'm no whiz-bang professional journalist, but I spot two glaring errors in the paragraphs above:
 
First, as I learned in the third grade (public school--in rural Texas, mind you), the potato is native to the Americas, so it would be bloody difficult for Kerry's putative ancestor to have introduced them.  And while I lack the vaunted training in research to be had at Columbia J-school, it only took me about 30 seconds with Google to discover a reference to potato farming in North America that predates Mr. McGregor by over a hundred years:

Kaishúcpenauk a white kind of roots about the bignes of hen egs & nere of that forme: their tast was not so good to our seeming as of the other, and therfore their place and manner of growing not so much cared for by vs: the inhabitãts notwithstanding vsed to boile & eate many.

Thomas Hariot, A briefe and true report of the new found land of Virginia (1590). 
 
Second, and more importantly, Kerry hasn't "always corrected" errors regarding his heritage--indeed, he's made some misstatements of his own.  This Slate article details several, including a March 18, 1986, declaration Kerry made on the floor of the Senate:

For those of us who are fortunate to share an Irish ancestry, we take great pride in the contributions that Irish-Americans …

and this statement he made in 1984:

As some of you may know, I am part-English and part-Irish. And when my Kerry ancestors first came over to Massachusetts from the old country to find work in the New World, it was my English ancestors who refused to hire them.

Now, I'm not suggesting for a moment that whether Kerry's long-dead ancestor invented the potato or whether Kerry has a drop or two of Irish blood matters one whit to whether he should be President (though potatoes have been an issue before, and whether Kerry lied is surely interesting).  But whether it matters or not, it would be easy enough for the AP to check out.  Who knows?  If the AP were scrupulously accurate with regard to printing minor factual claims that are easy to verify (or discredit), perhaps they'd be more believable when they publish major claims that are harder to check up on.  But such trivial details might distract them from their hagiography.