The Clinton campaign announced on Monday that Myrlie Evers-Williams, the widow of slain civil rights leader Medgar Evers, has endorsed the former Secretary of State in her bid to become the country’s first female president.

“After decades of slow but steady progress, the rights that my husband and many others fought and died for are threatened like never before,” Evers-Williams wrote in her endorsement statement. “It’s time to call out and say, take sides. You cannot sit back and observe. Become involved and do what you feel is best. Do not allow evil to overtake this America of ours.”

Former US President Bill Clinton joins Myrlie Evers-Williams, wife of the late civil rights activist Medgar Evers, during a wreath laying ceremony and service commemorating the 50th anniversary of the assassination of Evers, at Arlington National Cemetery in Arlington, Virginia, June 5, 2013. Evers was killed as he arrived at his home on June 12, 1963. SAUL LOEB/AFP/Getty Images AFP/Getty Images

Coming upon her 83rd birthday, Evers-Williams worked alongside her husband in the Civil Rights Era from the late 1950s to the early 1960s, continuing his fight for freedom and equality after he was assassinated in 1963. She became the chairperson of the NAACP in 1995, established the Medgar Evers Institute in Jackson, Mississippi – her home state – and became the first woman to deliver the invocation at a presidential inauguration once President Obama was reelected.

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Her endorsement follows another recently made by another Evers family member — Medgar Ever’s older brother. Charles Evers, 93, a former field secretary for the NAACP, is supporting Donald Trump.

"The main reason I like him, he shoots from the hip. He doesn't have written speeches and all that kinda stuff," Evers told NBC's Chris Jansing. "And he's a multi-billionaire. He didn't get there sitting waiting on welfare on the corner every month."

Evers, who switched to the Republican Party in 1980, endorsing Ronald Reagan, also praised Trump’s business bonafides and his ability to bring jobs and industry back to Mississippi — one of the poorest states in the nation.

When asked in an interview today whether she had a response to her brother-in-law's surprising endorsement, Evers-Williams replied, “It’s not printable.”

Her announcement comes on the eve of the presidential primary being held in Mississippi, where Evers-Williams resides and is a native. Clinton is also entering with a critical stretch of states won by black supporters in the 2016 presidential campaign.

“Medgar always knew that progress depended on protecting our access to the ballot box,” she wrote. Evers-Williams supports Clinton’s plan to restore provision of the Voting Rights Act to prevent voter ID laws, advocating the candidate’s plan to implement automatic universal voter registration.

The Voting Rights Act was initially signed into law in 1965 by President Lyndon B. Johnson lifting the bar that hindered African Americans from voting by removing restrictions such as poll taxes and literacy tests that had kept many black people from voting.

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However, as of May 13, 2015, at least 113 bills have introduced some kind of restrictive voting legislation in 33 states – more than half of the country. This statistic is a decline from 2012 numbers that reflect at least 180 restrictive bills being introduced in 41 states since the start of 2011.

Evers-Williams also emphasized her support for Clinton’s proposed plans criminal justice reform, which she contends are actually attainable. “Hillary Clinton has a plan to address gun violence with solutions that can actually be achieved.”

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