Harry Truman recognized the state of Israel in 1948. He famously did so over George Marshall's unusually vocal objections that this decision was politically motivated in view of the Jewish votes and lobby despite Truman's profound reverence for Marshall.
But how important a political issue was the creation of Israel domestically? Were enough voters concerned about it? Did it matter or was it at all significant in the margin for Truman's eventual victory?
The consensus I've seen is as follows:
It was not motivated by domestic affairs. Truman often took offense to this claim, according to Clark Clifford.
It was not crucial to domestic politics or a large issue. American Zionists definitely "annoyed" Truman extensively by lobbying him (though Clifford insists Truman didn't need his mind changed to begin with), but it wasn't a major election issue.
It was not significant for his margin of victory. The argument is often that he did it to win Jewish votes and take New York. But Truman lost New York anyways, and won the election.
There are obviously going to be disputes about this, but this is the succinct summary of what I've seen in my research on the topic.
From a friend versed in such things --
"electoral considerations, fear of Soviet pre-emption, and Secretary of State Marshall's neutrality were each important in Truman's thinking" -- Cohen, Michael Joseph. 1990. Truman and Israel. Berkeley: University of California Press.
He adds: Truman likely was trying to shore up support of domestic Zionist groups, which had soured a bit on him and his foreign policy. But, it was not as important an issue electorally as was beef, civil rights, and the cold war more generally. By beef, I also mean inflation and the standard and cost of living.
It's kind of complicated. On the one hand, there is a school of thought that says Truman did not see himself as courting the Zionist vote, merely fulfilling a 'biblical' duty - he even quipped that he was "Cyrus" - referring to the ending of the Babylonian Captivity. And there is ample evidence that it didn't go beyond this religious mission, for lack of a better term.
On the other hand, he and the Democratic party did want to court and keep the Jewish vote, especially in light of the Holocust which was very fresh in everyone's minds. SO to say that it did not play at least a little into the political calculus is a bit dodgy. It is most likely that it played a much lesser degree in his decision than some experts think (or that Truman was willign to admit).
[Here's] (http://www.trumanlibrary.org/whistlestop/study_collections/israel/large/index.php) the Truman Library online archives on the recognition of Israel.