Barstow also attempted to steal the 1855 Wisconsin gubernatorial election, and then illegitimately occupied the office of governor for the first three months of 1856 until compelled to resign.

Despite the ubiquity of the charges against him and a lengthy investigation by the Wisconsin Legislature, Barstow never faced criminal liability over these events.

Barstow was born in Plainfield, Connecticut, and was raised there, working on his family's farm and attending local schools.

William ran for sheriff of Milwaukee County in 1843 on the Democratic Party ticket, but was defeated by independent candidate Edward D. Holton.

In that election, Barstow was hurt by Democratic voter defections due to allegations he had packed the convention with supporters to secure his nomination.

[7] He fought a bitter campaign in the Democratic caucuses attempting to earn renomination, but, at the State Convention in 1851, he was defeated on the third ballot by Charles D. Robinson, of Brown County.

But his legal controversies continued, and, during the 1853 legislative session, Barstow's name was associated with several corrupt acts charged in the impeachment of Wisconsin Circuit Court Judge Levi Hubbell, and gave a deposition to the Legislature under subpoena.

At the state convention however, as Smith was unable to reach a majority after 7 ballots, he dropped out of the race and encouraged his delegates to support Barstow.

In the November 1853 general election, Barstow faced off against Free Soil candidate Edward D. Holton for the third time, defeating him again and earning 54% of the statewide vote.

As governor, Barstow supported the railroad to the Pacific and stood against the attempts of the Know-Nothing movement to undermine the citizenship of the foreign-born or slow down immigration.

[11] However, allegations of financial impropriety emerged again, this time related to the use of public school funds and improper influence on state-backed loans and other expenses appropriated by his allies in the Democrat-dominated 1854 Legislature.

When Barstow ran for reelection in 1855, he was initially declared the winner over his Republican opponent, Coles Bashford, by a mere 157 votes.

However, Bashford claimed the result was fraudulent, and it was soon substantiated that Barstow's win was due to forged election returns from nonexistent precincts in the sparsely populated northern part of the state, in addition to other irregularities such as two separate canvassing boards claiming legitimacy in Waupaca County and attempting to submit conflicting certifications.

On the same day, Bashford was also sworn in quietly as governor in the chambers of the Wisconsin Supreme Court by Chief Justice Edward V. Whiton.

After the outbreak of the American Civil War, Barstow wrote to General John C. Frémont, who had been named commander of the Department of the West, and offered to raise a regiment of cavalry.