Over the course of four recent spring days, Colorado hosted three 2020 Democratic presidential candidates — an unusual amount of political traffic so early in the election cycle for a swing state that is more familiar with a blitz during the run-up to Election Day. Get used to the unseasonable attention. Colorado Democrats and unaffiliated voters can expect to play a new and critical role in choosing the party’s next presidential nominee. Political experts in the first four nominating states suggest that the field of at least 18 candidates won’t be narrowed easily, which means the states that vote in early March 2020 — including Colorado — will have a crack at vetting them. While Colorado has not yet set a date for its presidential primary — the first since voters agreed in 2016 to abandon the caucus system — there is a strong possibility the state will vote on Super Tuesday, according to Colorado Democrats and state officials.