In 2016, Oliver took a deep dive into anti-abortion laws, and the many ways in which anti-choice lawmakers have attempted to restrict access to abortion without technically violating Roe v Wade. States have passed a flurry of anti-abortion laws since Donald Trump's election, and the current state of the Supreme Court means the issue will almost certainly be a high-profile one in the 2020 election.

The anti-vaccine movement has received a burst of attention lately, due largely to the recent measles outbreak and new state laws seeking to impose stricter vaccination requirements. As such, the 2020 candidates' views on vaccinations have come under a spotlight, and in 2017, Oliver explained exactly why the anti-vaccination movement is a legitimate public health hazard.

Much has been written about the recent rise of right-wing authoritarian attitudes in America and across the world. Oliver covered the topic in 2018, and given that several Democratic presidential candidates have accused Trump of having dictator-like qualities, authoritarianism will likely be on many voters' minds during the 2020 general election.

The United Nations estimates that there are 68.5 million refugees worldwide, and America's refugee policy continues to be a highly controversial and pressing policy issue. Back in 2015, Oliver looked at the facts behind the refugee crisis, and explained how many countries' asylum policies end up hurting migrants.

Democratic presidential candidates regularly take aim at Trump for the many documented lies, false statements, and mischaracterizations he's made during his short political career. In a 2017 segment, Oliver looked at Trump's complicated relationship with the truth, a subject that will no doubt be brought up regularly by Democrats during the 2020 campaign.

Relations between the United States and North Korea have oscillated wildly in the last several years. Trump made international news for becoming the first U.S. president to hold one-on-one negotiations with a North Korean head of state, but questions remain about what those talks actually accomplished, and tensions escalated in May 2019 when North Korea launched several missiles. Oliver's explainer is a great crash-course in the nuances of the mysterious, isolated country and its history with the United States.

In April 2019, after over a year of anticipation, Special Counsel Robert Mueller's report on Russian meddling in the 2016 election and possible obstruction of justice by Trump was finally released. But it's over 400 pages long, and around a third of it is redacted, leaving many people unclear on exactly what the report concluded. Oliver has an explainer on the topic ready, and it focuses on many of the small but important nuances in Mueller's report.

Student loans have become a central topic of debate in the Democratic primary, with many candidates pledging to fund free college for all Americans and, in some cases, cancel all student debt. In this 2014 segment, Oliver explained why student debt is so much harder to pay off than some other forms of debt, and accused for-profit colleges of bilking students out of tens of thousands of dollars in exchange for vocational training that's questionable at best.

Ever since the Supreme Court gutted the Voting Rights Act in 2013, a handful of Republican-led states have implemented policies that make it harder for eligible residents to vote. Multiple courts have found that these laws are intended to disenfranchise black voters from the electoral process, and independent research has shown that they do exactly that. Oliver devoted a segment to explaining how voting laws disenfranchise voters — and why voter fraud, which those laws are ostensibly aimed at preventing, is not a consequential problem in American elections.

The process by which parties nominate presidential candidates is incredibly complicated, with pages upon pages of rules determining exactly how each vote in the nominating contest is counted. In 2016, Oliver broke down how primaries and caucuses work, and that will be useful information to have as Democrats choose a candidate for 2020.

Election coverage generally focuses on candidates for president, governor, and Congress, but there's another elected office on the ballot that's hugely consequential for American policy: State attorney general. In this episode, Oliver explains why the position matters so much, which will be important for the 10 states that will elect state attorneys general in 2020.

If past is any indicator, Oliver's show will continue to be a source of news and comedic relief once the 2020 campaign properly kicks off. Until then, these past segments are a great way to stay informed and entertained during what's certain to be a brutal, lengthy presidential campaign season.