He won election to the United States House of Representatives in 1842 but was denied the party's nomination in 1844 due to his opposition to the annexation of Texas.

He attended Phillips Exeter Academy and graduated in 1827 from Bowdoin College, where he was a classmate of Franklin Pierce and a prominent member of the Athenian Society, a literary club.

This rule had been created by another New Hampshire representative, Charles G. Atherton and was intended to put a stop to anti-slavery petitions.

[2] Hale supported the Democratic candidates James K. Polk and George M. Dallas in the 1844 presidential election, and was renominated for his congressional seat without opposition.

The Democratic state convention was then reassembled in Concord under Pierce's leadership for the purpose of stripping Hale of his congressional nomination.

[3] The strong performance of the anti-slavery Free Soil Party resulted in no majority winner in the 1846 gubernatorial election or in seven out of twelve State Senate seats.

Accordingly, Hale's coalition of Whigs, Liberty Party members and Independent Democrats were able to join to win control of state government after the election.

It then elected Whig Anthony Colby as Governor (despite him winning just 32% of the vote to Democrat Jared W. Williams's 48%), Liberty Party member Joseph Cilley to a vacancy in the U.S. Senate, and Hale as Speaker of the State House.

[4] Hale was the only Senator to vote against the resolution tendering the thanks of Congress to Winfield Scott and Zachary Taylor for their victories in the Mexican–American War.

[5] In 1851, Hale served as counsel in the trials of anti-slavery activists that arose out of their forcible rescue of fugitive slave Shadrach Minkins from the custody of the United States Marshal in Boston.

[6] In March 1853, Hale was succeeded in the Senate by Democrat Charles G. Atherton and began practicing law in New York City.

Hale was elected to the Senate as a member of the new Republican Party in 1855, replacing Jared W. Williams, who had been appointed following the death of Charles G. Atherton.

Perry had accused Hale of violating his diplomatic privilege of importing free of duty merchandise for his official or personal use by putting some goods up for sale and pocketing the proceeds.

Longtime Washington journalist Benjamin Perley Poore wrote that Hale, as Senator in the late 1850s, "never failed to command attention":The keen shafts of the Southerners, aimed at him, fell harmlessly to his feet, and his wonderful good nature disarmed malicious opposition.

Those who felt that he had gone far astray in his political opinions did not accuse him of selfish motives, sordid purposes, or degraded intrigues.

His was the "chasseur" style of oratory—now skirmishing on the outskirts of an opponent's position, then rallying on some strange point, pouring in a rattling fire, standing firm against a charge, and ever displaying a perfect independence of action and a disregard of partisan drill.