The lead plaintiff in the lawsuit filed to keep Donald Trump off of Colorado's 2024 ballot is a 91-year-old fixture of the Colorado GOP.

Why it matters: The Colorado ballot case will come before the Supreme Court on Thursday after Colorado's highest court ruled in favor of disqualifying Trump. The case could have major ramifications for the ongoing legal challenges in other states.

• Norma Anderson's role in the suit highlights the ongoing resistance to Trump among some mainstream Republicans.

Anderson's background

A staunch Republican, Anderson had a 19-year career as a Colorado legislator and was the first woman to serve as majority leader in both the state House and state Senate.

• During her time in the legislature, Anderson was considered a moderate Republican who bucked the party line on issues like banning same sex marriage and requiring students to say the Pledge of Allegiance in schools, per the Colorado Sun.
• Anderson voted for third-party candidates in 2016 and 2020, according to the Washington Post. She even quit the Republican Party in 2018 because of Trump, before rejoining in 2021.

Involvement in the case

Last year, Anderson became the lead petitioner in a lawsuit filed by Colorado voters arguing Trump should not appear on the state ballot because his actions after losing the 2020 election violated the 14th Amendment's insurrection clause.

• "If that isn't insurrection, I don't know what is," Anderson told the Colorado Sun about the Jan. 6 Capitol riot.
• While a lower court allowed Trump to remain on the Colorado ballot, the Colorado Supreme Court booted Trump from the ballot in December after finding that the 14th Amendment's insurrection clause applied to Trump.
• Lawyers for Trump appealed the ruling to the U.S. Supreme Court, which agreed last month to hear the case.

The bottom line: Anderson told the Colorado Sun that she'll be watching the Supreme Court arguments closely and is hopeful a decision will be reached quickly.

• "I'm very happy I've done it," she said. "It does take courage."

Go deeper: Where efforts to disqualify Trump from 2024 ballot stand