Dwight Morrow (1873-1931) gave a speech in October 1930, during his successful campaign for U.S. Senate from New Jersey: “Any party which takes credit for the rain must not be surprised if its opponents blame it for the drouth.” Morrow was running as a Republican during an economic depression when he made the metaphoric statement.
 
The weather metaphor had been used before in politics. An Illinois newspaper reported in 1904: “The Democrats claim that the Republicans take credit for the rain which came from the heavens above, during the last four years.”
 
Another saying about politicians taking credit for prosperity—popular at about the same time—is “Prosperity is something created by businessmen for politicians to take credit for.”
     
   
Wikipedia: Dwight Morrow
Dwight Whitney Morrow (January 11, 1873 – October 5, 1931) was an American businessman, politician, and diplomat.
(...)
In 1930 he was elected as a Republican to the United States Senate to fill the vacancy caused by the resignation of Walter Evans Edge. At the same time he was elected for the full term commencing March 4, 1931. He served in the Senate from December 3, 1930, until his death in Englewood, New Jersey, on October 5, 1931.
   
3 September 1904, Rockford (IL) Republic, pg. 4, col. 1:
The Democrats claim that the Republicans take credit for the rain which came from the heavens above, during the last four years.
 
18 July 1908, Colorado Springs (CO) Gazette-Telegraph, “A Silly Plea,” pg. 4:
WE observe that it is urged in behalf of the aldermen that “if they are to be blamed for the lack of rain and snow this spring, then in all conscience they should be given credit for the rain which has been falling during the past week.”
 
Google News Archive
14 October 1930, Pittsburgh (PA) Press, pg. 8, col. 3:
MORROW HALTS
BOOM FOR 1932
Opens Senate Campaign by
Predicting Re-Election
of Hoover
By The United Press
NEWARK, N.J.—Dwight W. Morrow, hailed in the East as a presidential possibility in 1932, believes President Hoover will be renominated and re-elected.
(...)
Morrow met the “prosperity” issue raised by his Democratic opponent, State Senator Alexander Simpson. Speaking of the economic depression, he said he recognized the tendencies of political parties to exaggerate the accomplishments of their own administrations and deprecate achievements of their opponents.
 
“Any party which takes credit for the rain must not be surprised if its opponents blame it for the drouth,” he said.
   
Google Books
The Toastmaster’s Handbook
By Herbert V. Prochnow
New York, NY: Prentice-Hall
1949
Pg. 263:
Any party which takes credit for the rain must not be surprised if its opponents blame it for the drought. Morrow.
 
Google News Archive
19 September 1992, Spartanburg (SC) Herald-Journal, “On Language: Here’s tjhe way the poll bounces” by William Safire, pg. A10, col. 4:
WORDS OF WISDOM
Phrase junkies are always on the lookout for political axioms, adages and proverbs.
 
Bert Lance’s “If it ain’t broke, don’t fix it” has become a source of inspiration to anti-activists. Dwight Morrow’s “Any party which takes credit for the rain must not be surprised if its opponents blame it for the drought” is being ruefully repeated by supporters of George Bush.