Vice President Kamala Harris’ likely ballot matchup this fall against former President Donald Trump will echo her time in the Senate, where she carved out an opposition to his first term in office with a prosecutorial bent.

Her first speech on the Senate floor was in opposition to Trump’s nominee for secretary of Education. Many of her most high-profile moments in the chamber came during questioning of Trump nominees or officials, and several of her most prominent bills and resolutions were a direct response to Trump’s policies on border security and more.

Even where Harris’ legislative priorities as a senator did not immediately respond to Trump’s actions, they are set to collide with the Republican platform on issues ranging from criminal justice policy to abortion and LGBT protections.

And Harris leveraged her experience as a prosecutor and California attorney general for her positions on criminal justice issues and an assertive courtroom style to create some of her most high-profile moments in the Senate, scrapping with Trump administration officials and nominees to make bigger points.

In one exchange, in 2019 she questioned William Barr, the nominee for attorney general, when she repeatedly asked about whether anyone in the White House had pressured him to open criminal investigations into political enemies.

“Has the president or anyone at the White House ever asked or suggested that you open an investigation of anyone?” Harris asked. She then sparred with Barr in a heated exchange over the meaning of “suggested,” and later asked the Justice Department watchdog to open an investigate into the possibility.

Sen. Martin Heinrich, D-N.M., who served with Harris on the Senate Intelligence Committee, told reporters she was a “consummate prosecutor” in her questioning of witnesses. Even though Harris was a fairly junior senator, Heinrich said she crafted pressing questions during hearings such as one with former Attorney General Jeff Sessions.

“Despite the fact that she was very junior on the committee, when we got to her, she still had really effective questions that really visibly rattled Jeff Sessions in that case,” Heinrich said.

In the 2018 confirmation hearing for Supreme Court Justice Brett M. Kavanaugh, Harris highlighted the difference between the parties on abortion, with a question about “any laws that give government the power to make decisions about the male body.”

Kavanaugh eventually answered that he did not know of any.

Legislation

During her Senate tenure Harris introduced more than 100 pieces of legislation and resolutions, ranging from a resolution condemning hate crimes, to promoting telehealth to several bills heightening penalties for revenge porn.

Although none made it into law during her time in the chamber, those bills and the ones she co-sponsored and voted for showed a senator on a collision course with the modern Republican party.

Republicans have made immigration a major issue in this year’s election, including accusing Harris of being partially responsible for a surge in migrants crossing the U.S. border with Mexico.

During her tenure in the Senate, Harris backed prominent changes to immigration law, such as two versions of a bill to give a path to citizenship for participants of the Deferred Action for Childhood Arrivals program.

As a member of the Senate Homeland Security and Governmental Affairs Committee, Harris frequently criticized Trump’s family separation policy and immigration approach overall.

She also introduced legislation with her own tweaks to immigration policy, including legislation to provide a right to an attorney to people fighting deportation and another bill to limit the expansion of immigrant detention facilities.

The Republican platform listed opposition to numerous mention that Harris supported during her Senate career.

In particular, the platform mentioned “terminating the Socialist Green New Deal,” a proposal to fight climate change originally introduced by Sen. Edward J. Markey, D-Mass., and Rep. Alexandria Ocasio-Cortez, D-N.Y., which Harris backed.

Environment and more

Harris also introduced several bills to change how the federal government handled environmental issues, including one while running for vice president that would change how federal agencies evaluate the environmental impact of their decisions on minority and underprivileged communities.

She introduced legislation that would expand exceptions in the federal religious conscience law known as the Religious Freedom Restoration Act. The bill, which did not advance, would have prevented individuals from raising religious exemptions to providing housing, access to public accommodations and employment.

Republicans have used RFRA as a central plank of their arguments against federal protections for abortion and LGBT individuals in public accommodations.

The law surfaced as part of oral arguments over Idaho’s ban on almost all abortion procedures at the Supreme Court this past term and has factored into conservative objections to federal policies ranging from contraceptive coverage to website design for same-sex weddings.

Additionally, the Republican platform would withdraw any federal funding for “Left-wing Gender Insanity,” including gender affirming surgery or school support for transgender children.

Similarly, vice presidential candidate Sen. JD Vance, R-Ohio, signed onto an October letter with Sen. Marco Rubio, R-Fla., opposing the addition of a question on sexual orientation and gender identity to a census survey.

The Census Bureau has proposed asking the question starting later this decade on the American Community Survey.

Harris introduced a bill in 2018 which would have mandated the Census Bureau ask that question on that survey and in the 2030 census.

Harris also sponsored a variety of bills to increase diversity in representation across government and American society, including a bill that would require that the Federal Reserve adopt a version of the “Rooney Rule” to interview minority candidates for Reserve Bank presidencies.

She also backed legislation to curb racially disparate outcomes in COVID-19 treatment and increase anti-bias training surrounding the disease.

That approach is likely to clash with the Trump campaign, which has promised to end all federal anti-bias training, and decried efforts to address systemic racism as “woke.”

At least one piece of legislation from Harris has since made it into law. She, along with Sen. Cory Booker, D-N.J., backed legislation that would make lynching a federal hate crime. The legislation eventually became law during the Biden administration.

Jessie Hellmann and Ariel Cohen contributed to this report.