Upvote:5
Apparently the mistake was an electoral appeal that urged Americans to vote Democratic because a vote for Republicans would
". . . be interpreted on the other side of the water as a repudiation of my leadership." .
This achieved the opposite of the desired effect, losing the election for the Democrats, as the letter was (correctly) perceived as an unwarranted slight on the Republicans' patriotism.
Source: http://www.canadafreepress.com/index.php/article/29553