Born in Dorchester, Gardner was a dry goods merchant from Boston active in the local Whig Party in the early 1850s.

With the sudden and secretive rise of the nativist Know Nothings in 1854, Gardner opportunistically[2] repudiated previously-held positions, and joined the movement, winning a landslide victory over Whig Emory Washburn.

[3] His grandfather, also named Henry Gardner, was a well-respected Harvard graduate, was politically active during the American Revolution and served as the state's treasurer 1774–82.

[7] This shift in position was fairly radical on Gardner's part, and was viewed by contemporaries and recent historians as politically opportunist.

The speech focused almost to exclusion on nativist issues, and included hyperbolic claims that the level of immigration was reaching crisis proportions.

Gardner notably omitted popular substantive reform issues such as the ten-hour workday, and also avoided the contentious subject of slavery.

A board of insurance with broad powers of inspection was created; bankruptcy laws were changed to benefit lower-class individuals; imprisonment for debt was abolished.

Vaccinations were mandated for all school children, women were given the right to own property on their own, and exempted from responsibility for their husbands' debts; and restrictions were placed on child labor.

[13] Cities and towns were authorized to engage in a wide variety of civic improvements, including the building of highways, gas, water, and sewer lines, and public transport facilities such as docks and wharves.

[16] One reform that was immediately a subject of controversy was a harsh prohibition law, which criminalized the service of a glass of grog with a six-month jail sentence.

The bill, signed into law by Gardner, was immediately protested, and legislators who passed it were later criticized for charging bar tabs to the state when they traveled.

Joseph Hiss, one of the principal investigators, was reported to have made lewd remarks to nuns in these establishments, and was later found to engage in drinking and the hiring of prostitutes.

A third Bill of Address to remove Loring from office was later approved by Gardner's Republican successor, Nathaniel Prentice Banks.

[24] Minority parties in the legislature sought to weaken the bill, but its major provisions, including rights of habeas corpus, jury trial, and state-funded defense, survived.

Prominent antislavery Know Nothing supporters in Massachusetts, including Henry Wilson, began another attempt (after having failed in 1854) to form a party with abolition as a major focus.

With the new plurality voting rule in effect, Gardner won the election,[29] but the split (and disaffection in some circles with the Know Nothing agenda) cost him support from former Free Soilers and Democrats.