Hilary Clinton did actually join politics until after her husband’s presidency unless you count her time as First Lady of Arkansas and First Lady of the United States as being a political career. If you don’t, then her political career began in 2001. At this time, she was elected as the United States senator from New York. She would be that senator from 2001 until 2009.
Before her last year as a senator, she campaigned for the presidency, but she did not win. She didn’t win her party’s candidacy. Instead, Barack Obama became the presidential candidate for the Democratic Party. Then she continued her political career by becoming the secretary of state in 2009 and finished it in 2013. Then she tried to become president again in 2016 when she campaigned again.