In 2014, Diamond successfully ran for the 102nd district to replace Representative RoseMarie Swanger, who spent four terms in the state House after being backed by Diamond's organization. The campaign was contentious; Diamond's supporters filed legal challenges against the campaigns of Joe Eisenhauer and Wanda Bechtold, who sought the Republican nomination, and successfully got their names removed from the primary ballot (due to a failure to timely file financial disclosure forms and a failure to obtain enough signatures, respectively). As a result of these challenges, Diamond was the only candidate on the ballot in the May primary, although Bechtold ran an unsuccessful write-in campaign. Diamond won the general election with 45 percent of the vote, defeating Democrat Jake Long (who received 26%), independent Robert McAteer (who received almost 23% of the vote), and write-in candidate Bechtold. (Both McAteer and Bechtold indicated that they would serve as Republicans if elected.) Diamond won reelection in 2016 with 70% of the vote, won reelection unopposed in 2018, and won reelection in 2020 with 70.8% of the vote. Tenure and controversies COVID-19 In 2020, during the COVID-19 pandemic, Diamond opposed public-health measures to prevent the spread of the virus. Diamond opposed Governor Tom Wolf's statewide mandate requiring the wearing of face coverings in indoor public places (saying that the order promoted "hatred and intolerance across Pennsylvania"), opposed Wolf's closure of non-essential businesses, and called on Wolf to fire Dr. Rachel Levine, the Pennsylvania secretary of health. Diamond spoke at anti-shutdown rallies at the State Capitol and sponsored a resolution seeking to reverse Wolf's closure of nonessential businesses; the resolution passed the Pennsylvania General Assembly, but the Pennsylvania Supreme Court ruled that it had no effect. In May 2020, Diamond bragged on social media about shopping without a face covering. In July 2020, Diamond mocked a statement against discrimination against LGBT people issued by Levine, who is transgender, by copying-and-pasting her statement and replacing the term "LGBTQ" with the word "unmasked" to allege discrimination against what he called the "unmasked community" (people who refuse to wear masks during the COVID-19 pandemic). Governor Tom Wolf condemned Diamond's statement and said, "We need the Republicans to stop spreading misinformation to the general public, and we badly need them to be more responsible and more responsive to the health and wellbeing of all Pennsylvanians. This dangerous, reckless behavior is not welcome in Pennsylvania." Wolf called for the legislature