PORTLAND — Tuesday, April 28, is the deadline to register to vote in Oregon’s May primary. It’s also your last chance to switch from being an unaffiliated voter to registering with one of the major parties, even temporarily. That’s a must-do if you have an itch to vote for Joe Biden, the all-around-endorsed Democrat, one of his opponents who have quit the race, or Donald Trump, the Republicans’ triumphant re-nominee.

Oregonians who register to vote as members of minor parties or no party at all still can vote in city and county elections and on ballot measures. But they won’t see Trump or Biden’s names on their ballot, nor the names of candidates for the Legislature or Oregon secretary of state or other statewide offices.

The purpose of a primary is to nominate each party’s top choice for the general election contest in the fall, so voters who aren’t registered with a party don’t get a say at this stage.

Voters who are independent of any party get no say in Oregon’s partisan primary races, said Andrea Chiapella, legislative and communications director for the Oregon Secretary of State’s Office. Minor parties have their own systems of voting that aren’t run through the state elections office, she said, such as this one for the Independent Party of Oregon.

For registered Democrats, the primary ballot could offer interesting choices in the presidential race as well as for many legislative seats and Oregon secretary of state. Even though Biden’s challengers have all conceded he’s clinched the Democratic nomination and endorsed him, Oregon Democrats will still see multiple candidates on their ballot. Listed as choices in the race for president will be Biden, Tulsi Gabbard, Bernie Sanders and Elizabeth Warren, all of whom qualified at Oregon’s deadline to print ballots and begin getting them to overseas voters.

As with so many other aspects of Oregon’s vote-by-mail system, you can register to vote or change your party registration safely from the comfort of your own home, as long as you are at least 16 years old, have access to the internet and possess a valid Oregon driver’s license, driver permit or ID card that indicates you are a citizen.