Utah is often referred to a "the reddest of the red states", a phrase referring to the current dominance of the Republican Party in the state's politics. Progressives and Democrats regularly harp on this statement as if it's the way it's always been. This characterization, however, is far from the truth.
Even prior to statehood, Utah took some notably progressive steps. Women were granted the right to vote in the territory in 1870, decades before the 19th Amendment made this right universal. (The irony here is that this was seen as a way to vote out polygamy. Instead, the opposite happened and Congress stripped women of the right to vote in 1887.) Despite the control of the houses of Congress being split between Republicans and Democrats, the GOP had been leading the push against polygamy most ardently and alienated many Utahns. As a result, the 2nd State Legislature was almost exclusively comprised of Democrats. This solid voting block reportedly caused LDS church authorities to divide congregations in half and declare that one half was Democrats and the other were Republicans. The Socialist Party was also very popular in early statehood, electing over 100 candidates during the first two decades of Utah's existence.
Even through the mid-20th century, the legislature has not been solidly in any kind of Republican stranglehold. The 35th State Legislature had a 1-vote Republican majority in the Senate and a 2-vote majority in the House. Prior to that election, Democrats controller both houses, a US Senate seat, both US House seats and a majority of county offices. This is the same state that gave FDR large majorities in every election he ran in despite the objections of Heber J. Grant, prophet of the LDS church. (It should be noted that Grant was a life-long Democrat making his objections to FDR and the New Deal all the more complex and interesting.) It would appear that Utah has a long and storied history of political diversity unconstrained by ecclesiastical authority.
So why is the state now so heavily dominated by the Republican Party? Prior to the 1960s, each party consisted of factions constantly struggling for dominance. Truman had to fend off both isolationists in the Republican Party and pro-Soviets in his own party to come up with a Cold War strategy. Eisenhower had to do battle with Robert Taft to keep NATO going. Each party had distinct groups of both liberal and conservative members with a variety of views. This started changing the late 60s and early 70s.
LBJ had managed to infuriate all but a small wing of the Democratic Party leading up to the 1968 Democratic Convention, most of the rage centered around the Vietnam War and the multiple race riots in urban areas. Johnson's own faction dedicated to the current policy of containment had dwindled to near nothingness while the hawks in the party that demanded military victory were greatly outnumbered by doves. George Wallace also took a substantial part of the party away that year with a third-party run for President. The Democratic Party came to be defined as the anti-war party with a large membership of intellectuals and students.
This trend continued in 1972 with the nomination of George McGovern by the anti-war and anti-elitist faction of the Democrats, pushing out big business interests that had been represented by Hubert Humphrey. This positioning as the party of the oppressed saw friendly relationships with feminists and black power groups as well, things that alienated social conservatives. The real nail in the coffin came with the enthusiastic embrace of the 1973 Roe v Wade decision.
These social issues would not have been a defining mark of either party if not for the increased drive for ideological purity by both sides. Republicans started purging liberals starting in the days of Barry Goldwater and the 1968 party convention is where Democrats started to get rid of conservatives. By making no room for multiple factions, it was a natural move for social conservatives to jump to the Republicans, a move echoed not just in Utah but also in Southern states and the rural Midwest. In exchange, Democrats took in minorities, women and a large section of urban population.
Democrats today often bemoan the single-party dominance of our state, yet they are lying the bed they started making four decades ago. Don't like it? Start making places for libertarians, socially conservative moderates and fiscally conservative progressives. Truly be a party of inclusion as opposed to just talking the talk.