Just days ahead of the requested response date, most nonpartisan mail ballot voters haven't notified the county whether they'll vote for president in the primary election.
Voters who are registered as having no party preference must request a ballot or re-register their affiliation if they want to vote for a presidential candidate in March.
San Diego County Registrar of Voters Michael Vu is urging nonpartisan San Diegans who vote by mail to make a choice by Monday so they'll receive the correct ballot on time.
Vu said his office sent informational cards to the county's 380,000 nonpartisan mail voters with their options to vote for president, but only 49,000 took action.
"Do not procrastinate. This is one of the most complex elections that we have," Vu said.
The Democratic, American Independent and Libertarian parties allow nonpartisan voters to simply request a ballot, but that version of the Democratic ballot won't include central committee candidates.
If nonpartisan San Diegans want to cast a ballot for a Republican, Green or Peace and Freedom candidate, they'll need to register with that party.
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The Registrar of Voters' office partnered with the Independent Voter Project, League of Women Voters San Diego and Alliance San Diego to conduct outreach.
"Regardless of party affiliation, we need to make sure that more people participate in our civic process," Alliance San Diego Executive Director Andrea Guerrero said. "That is how we build a strong and thriving democracy.''
Vu said voters who submit their request of a partisan ballot after the Jan. 6 deadline may still receive a nonpartisan ballot in the mail, potentially causing confusion and delaying them from voting for the candidate of their choice. He also warned against deciding at a voting location on Election Day because the process could create long lines for other voters.
"I would say that's a measure of last resort. Don't use that as a rule of thumb come Election Day," Vu said.
Vu said the process could further be complicated by the many versions of ballots required at precincts. They must have ballots for all political preferences and for the various local races for every jurisdiction in the county in English, Spanish, Filipino, Vietnamese and Chinese.
"I anticipate anywhere between 10,000 to 12,000 variations of the ballot," Vu said.
The registrar's office also mailed flyers to all 1.8 million registered voters with their preferences so they can make changes ahead of the Feb. 18 voter registration deadline.
