The 1966 Maryland gubernatorial election was held on November 8, 1966. Incumbent Democratic governor J. Millard Tawes was unable to seek a third term in office. In the election to succeed him, George P. Mahoney, a controversial segregationist, emerged from the Democratic primary due to splintered support for the two major candidates. Baltimore County Executive Spiro Agnew, was nominated by the Republican Party as their gubernatorial candidate. Mahoney and Agnew squared off, along with independent candidate Hyman A. Pressman. Ultimately, Agnew was victorious over Mahoney, with Pressman a distant third. This year was the last time that the state of Maryland elected a Republican governor until 2002. Agnew was later nominated for vice president by the Republican National Convention, per Richard Nixon's request, in 1968, an election he and Nixon won.
As of 2023[ [update]] this marks the last time the following Independent city and Counties have voted Republican in a gubernatorial election: Baltimore City, Montgomery, and Prince George's.
Democratic primary.
Results.
! scope="col" colspan="2" style="width: 15em" |Party
! scope="col" style="width: 17em" |Candidate
! scope="col" style="width: 5em" |Votes
! scope="col" style="width: 3.5em" |%
! colspan="3" style="text-align:right;" | Total votes
Republican primary.
Results.
! scope="col" colspan="2" style="width: 15em" |Party
! scope="col" style="width: 17em" |Candidate
! scope="col" style="width: 5em" |Votes
! scope="col" style="width: 3.5em" |%
! colspan="3" style="text-align:right;" | Total votes
General election.
Campaign.
Baltimore paving contractor and perennial candidate George P. Mahoney won the Democratic primary on a segregationist platform, which was possible due to the presence of several strong candidates. Mahoney's slogan, "Your home is your castle--protect it", as well as his stance on many civil rights issues, prompted Baltimore City Comptroller Hyman A. Pressman to enter the race as an independent candidate. Mahoney's controversial stances caused many in the Maryland Democratic Party to split their support between Agnew, which was possible due to his socially progressive views, and Pressman, which enabled Agnew to win the election with a plurality, taking 70% of the black vote.
Results.
! scope="col" colspan="2" style="width: 130px"|Party
! scope="col" style="width: 17em"|Candidate
! scope="col" style="width: 5em"|Votes
! scope="col" style="width: 3.5em"|%
! scope="col" style="width: 3.5em"| ;templatestyles src="Template:Tooltip/styles.css" / ;±%
 
! colspan="3" style="text-align: right; margin-right: 0.5em" | Majority
! colspan="3" style="text-align: right; margin-right: 0.5em" scope=row | Turnout
! style="text-align:right;" | Swing
References.
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