In 1787, Hamilton served as assemblyman from in the and was chosen as a delegate for the by his father-in-law Philip Schuyler.:191 Even though Hamilton had been a leader in calling for a new Constitutional Convention, his direct influence at the Convention itself was quite limited. Governor 's faction in the New York legislature had chosen New York's other two delegates, and , and both of them opposed Hamilton's goal of a strong national government.:227–28 Thus, whenever the other two members of the New York delegation were present, they decided New York's vote, to ensure that there were no major alterations to the Articles of Confederation.:195
Early in the Convention he made a speech proposing a President-for-Life; it had no effect upon the deliberations of the convention. to have an elected President and elected who would serve for life, contingent upon "good behavior" and subject to removal for corruption or abuse; this idea contributed later to the hostile view of Hamilton as a monarchist sympathizer, held by .:232 According to Madison's notes, Hamilton said in regards to the executive, "The English model was the only good one on this subject. The hereditary interest of the king was so interwoven with that of the nation, and his personal emoluments so great, that he was placed above the danger of being corrupted from abroad...Let one executive be appointed for life who dares execute his powers."
Hamilton argued, "And let me observe that an executive is less dangerous to the liberties of the people when in office during life than for seven years. It may be said this constitutes as an elective monarchy...But by making the executive subject to impeachment, the term 'monarchy' cannot apply..." During the convention, Hamilton constructed a draft for the Constitution based on the convention debates, but he never presented it. This draft had most of the features of the actual Constitution. In this draft, the Senate was to be elected in proportion to the population, being two-fifths the size of the House, and the President and Senators were to be elected through complex multistage elections, in which chosen electors would elect smaller bodies of electors; they would hold office for life, but were removable for misconduct. The President would have an absolute veto. The was to have immediate jurisdiction over all involving the United States, and state governors were to be appointed by the federal government.
At the end of the Convention, Hamilton was still not content with the final Constitution, but signed it anyway as a vast improvement over the Articles of Confederation, and urged his fellow delegates to do so also. Since the other two members of the New York delegation, Lansing and Yates, had already withdrawn, Hamilton was the only New York signer to the United States Constitution.:206 He then took a highly active part in the successful campaign for the document's ratification in New York in 1788, which was a crucial step in its national ratification. He first used the popularity of the Constitution by the masses to compel George Clinton to sign, but was unsuccessful. The state convention in Poughkeepsie in June 1788 pitted Hamilton, Jay, , , and against the Clintonian faction led by , Lansing, Yates, and .
Hamilton's faction were against any conditional ratification, under the impression that New York would not be accepted into the Union, while Clinton's faction wanted to amend the Constitution, while maintaining the state's right to secede if their attempts failed. During the state convention, New Hampshire and Virginia becoming the ninth and tenth states to ratify the Constitution, respectively, had ensured any adjournment would not happen and a compromise would have to be reached. Hamilton's arguments used for the ratifications were largely iterations of work from The Federalist Papers, and Smith eventually went for ratification, though it was more out of necessity than Hamilton's rhetoric. The vote in the state constitution was ratified 30 to 27, on July 26, 1788.
In 1788, Hamilton served yet another term in what proved to be the last session of the under the . When the term of Philip Schuyler was up in 1791, elected in his place was the attorney general of New York, one . Hamilton blamed Burr for this result, and ill characterizations of Burr appear in his correspondence thereafter. The two men did work together from time to time thereafter on various projects, including Hamilton's army of 1798 and the .
