Crane was appointed October 12, 1904 by Governor
John L. Bates to continue the U.S. Senate term of the late
George F. Hoar. He was then elected in a January 18, 1905 special election to finish the term. He was re-elected in 1907 and served until 1913. As Senator, Crane was famous for his lack of public statements and behind-the-scenes maneuvering. Senator from New York
Chauncey Depew wrote that Crane "never made a speech. I do not remember that he made a motion. Yet he was the most influential member of that body."
Calvin Coolidge observed that "his influence was very great, but that it was of an intangible nature." He was an opponent of
reciprocity (reduced tariffs) with
Canada and the
Dominion of Newfoundland, working to water down provisions of a proposed treaty. In 1905, Crane may have been instrumental in denying Democrat
William L. Douglas a second term as governor. Douglas, a successful and widely-known shoe manufacturer, won election in 1904 with labor support and high name recognition. According to
Charles S. Hamlin, Republicans discovered that Douglas had apparently fraudulently acquired an
honorable discharge after deserting during the Civil War. The
quid pro quo for this information not being revealed, supposedly engineered by Crane and Senator Henry Cabot Lodge, was that Douglas would not run again. In the
1908 presidential election, Crane expressed early support for
William Howard Taft, but later came to oppose Taft, believing him a weak candidate. This placed him in opposition to fellow Senator
Henry Cabot Lodge, a strong Taft supporter, in a struggle for control of the state delegation to
the national convention. Crane preferred to leave the delegates without formal instruction as to how they should vote, while Lodge preferred that they be required to pledge for Taft. Crane won Lodge's support for an uncommitted delegation in exchange for the election of
John Davis Long, a Taft supporter, as an at-large delegate. Crane ultimately reconciled with both Taft and Lodge. He became one of Taft's closest advisors after his election and worked to secure Lodge's reelection in 1911. In the 1912 general election, the Republican Party was divided by
Roosevelt's defection, and conservative elements of the party dominated the state legislature's caucus. This resulted in the election in early 1913 of the ultraconservative
John W. Weeks over Crane for the Senate seat. ==Personal life and death==