While reading, I've come across a lot of the US State Department's concerns from the area, where they were convinced the elections would be like elections in a police state, with people being forced to vote a certain way. I also came across the Tito-Subasic Agreement, which was used to only allow Communists to run for office. However, Churchill also seems to have recognised Tito's legitimacy as an interim leader in Yugoslavia after the war, so I'm curious what the relationship of him and his actual election was. Was Tito elected in a fair election? What are some good sources to read more about the 1945 Yugoslav elections?
It would be a good start to see how the elections were set up and conducted. Communist Party didn't directly participate, but it did dominate within all organisations represented in People's Front. While in principle other political organisations were allowed, very strict restrictions, mostly placed through very wide definition of what constituted collaboration, made it impossible for another party or coalition to appear in elections independent of PF. So in the elections themselves there were two options for voters: PF or so called blank list (a vote for no-one). Pre-election PF absolutely dominated in media. Furthermore, the method of voting was by placing a ball into one box or another, so not really a secret ballot. Finally, a significant number of potential opposition voters were denied voting rights or political participation on the grounds of either collaboration or that they would "work against the heritage of People's Liberation Struggle". Those made some 6% of electorate, but in some areas it went as high as 14%. At the same time, many youth under 18 were granted voting rights due to their participation in the war. In short, CP was determined and explicit in that, having won the war they don't intend to lose the elections. Same sentiment was even publicly presented, referring to PF as CP was rarely if at all written about at the time.
Elections therefore were far from fair. Most estimated, at the time and later, from either Yugoslav or western sources, agree that PF would almost certainly win even in fair elections. But that doesn't make them fair.
According to first Tito-Šubašić agreement (June 1944) royal government in exile recognized the federal state, provisional rule of National liberation committees, and People's Liberation Army as a legitimate Yugoslav army. In return, Tito agreed not to raise the issue of monarchy until after the liberation. Second agreement (November 1944) forbid kind Pavle I from entering Yugoslavia until the issue of monarchy was settled in elections, joint Provisional government was formed (including non-communist ministers) and free activity of political parties was guaranteed (however, soon subverted by various means).
I don't know what I could recommend on election in English, but relevant parts of The Three Yugoslavias by Sabina Ramet and especially Power and Persuasion by Carol Lilly would likely provide enough about the elections.