“NOTHING SHORT of genuinely scary.”

It’s hard to disagree with that description by former White House press secretary Robert Gibbs of protesters storming the stage Tuesday night at Joe Biden’s rally in California. While Mr. Biden did not appear to be in danger from the anti-dairy activists, their ability to get so close to him as he celebrated his wins in the Super Tuesday Democratic primaries evoked terrible memories of the night in 1968 when another candidate for president, Robert F. Kennedy, was assassinated following his victory in the California primary. What happened Tuesday underscores the need for the Trump administration to authorize immediate Secret Service protection for the Democratic candidates.

Mr. Biden was just a few words into his victory speech when a protester waving a placard rushed the stage. The intruder came within a few feet of the former vice president before his wife, Jill Biden, stepped in and blocked her. Seconds later, another protester stormed the stage and was pushed back by Ms. Biden and Biden senior adviser Symone D. Sanders. “We’re okay. We’re okay,” Ms. Biden said after the protesters — from the same group that previously interrupted events of Sens. Bernie Sanders (I-Vt.) and Elizabeth Warren (D-Mass.) — were removed.

Who gets Secret Service protection has been a recurring question in presidential campaigns. After Kennedy’s assassination, the law was changed to automatically authorize protection for major presidential and vice-presidential candidates and their spouses within 120 days of the general election. But in practice, there have been instances of candidates receiving protection much earlier in the campaign cycle. Then-Sen. Barack Obama, for example, received protection a year and a half prior to the presidential election.

The decision is made not by the Secret Service but by the secretary of homeland security based on certain criteria and after consultation with an advisory committee that includes majority and minority leadership from the House and Senate. The decision on whether to accept protection lies with the candidates; by law, only sitting presidents and vice presidents can’t decline protection.

The chairman of the House Committee on Homeland Security on Wednesday called on the Trump administration to immediately undertake the process to determine whether any Democratic candidates should be afforded protection, noting that Mr. Biden and Mr. Sanders appear to satisfy several of the criteria. “Americans deserve to know that the major candidates for President are protected from all threats to their safety,” Rep. Bennie Thompson (D-Miss.) wrote to acting homeland security secretary Chad Wolf. In light of Tuesday’s disturbing incident, the Trump administration should heed Mr. Thompson’s call for prompt action and take the steps needed to ensure the safety of the presidential candidates.

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