Kamala Harris’s vice presidency was already shaping up to be a uniquely consequential one. Now Democratic control of the Senate has propelled her to the front of the political scene, where she’ll be breaking ties and giving President Joe Biden’s legislative agenda a chance at life.

Being part of the president’s deliberative process is already a major step for a vice president—before Walter Mondale, the office lacked any precedent or model for West Wing power-sharing. Now Biden and Harris may offer a vision of an even more empowered vice president, able to champion legislation herself, use her bully pulpit, and potentially break ties to protect her own policy priorities. No vice president has done all of that before, but Harris could.

An evenly split Senate is rare, but party leaders have worked out power-sharing agreements before to ensure smooth operations, most recently after the 2000 election. Tie-breaking votes are more common (vice presidents have cast them 268 times), and have happened more frequently in the past 20 years than they used to.

That uptick coincided with the emergence of the modern vice presidency, Joel Goldstein, a vice-presidential scholar, told me. Though originally considered a legislative officer, since Richard Nixon’s term, the vice president has served primarily as a member of the executive branch. Modern veeps rarely spend time in the Senate, except on ceremonial occasions.

The partisan makeup of the chamber also lends itself to more ties, Goldstein said: Former Vice President Dick Cheney cast most of his eight votes during his first term, when the Senate was either evenly split or closely divided. The closest the Senate ever got to a tie while Biden was vice president was from 2011 to 2013, with 53 Democrats and 47 Republicans—and he never cast a tie-breaking vote.

Ties are also more common because of the sorting of parties into homogenous ideological groups, Goldstein told me. “The Senate is more evenly split, and the fact that politics has become increasingly polarized” means that fewer senators are willing to cross party lines, and more contentious votes are taken. In addition, the slow rollback of the filibuster means that fewer actions require more than a simple majority—which a vice president can help achieve. Of the 13 ties Mike Pence had to break, half were to confirm Cabinet-level, judicial, or ambassadorial nominations—votes that vice presidents hadn’t had to cast before, because nominations were less disputed. That collection includes the votes to confirm Betsy DeVos as secretary of education in 2017 and Jonathan Allen Kobes as a federal circuit judge in 2018. In each case, increased partisanship set up the vice president to play a major role in advancing the administration’s goals.

Harris may have to break even more ties than Pence did—especially on Cabinet picks, coronavirus-relief bills, and electoral reforms, all of which are priorities for the Democrats, as my colleague Elaine Godfrey has reported. Harris may end up being the public face of these deliberations—unless relatively moderate senators such as Joe Manchin, Susan Collins, or Lisa Murkowski cross party lines.

Harris will be constrained by loyalty to Biden on these votes; television shows such as Veep and The West Wing have conjured images of rogue vice presidents turning on their governing partners for key votes, but that has rarely happened—only one vice president, John C. Calhoun, has broken a tie by voting against the president, dooming Andrew Jackson’s nomination of Martin Van Buren to be the ambassador to Great Britain. Calhoun, who chose not to break a tie on a different judicial nomination in order to stymie Jackson, also holds the record for most ties broken.

A vice president voting against a president’s wishes would have been more likely in the 18th and 19th century, Goldstein told me, because deputies weren’t always loyal to the president, either because they weren’t from the same party (like Adams and Jefferson) or because they weren’t in the president’s inner circle (like Kennedy and Johnson). Neither is true for Harris. She hopes to follow Biden’s example as vice president, a Harris aide told me, acting as a full governing partner rather than sticking to a limited set of portfolio issues. (The aide spoke on the condition of anonymity because she was not authorized to discuss administration matters on the record.)

And though vice presidents cast tie-breaking votes as representatives of the administration, they can still claim those votes as part of their political résumés: Should a new version of the CARES Act or the Voting Rights Act face a tie in the Senate, Harris could claim responsibility for its passage.

There is a downside to more tie-breaking votes: Harris will have to keep her calendar clear to actually cast those votes—and finicky congressional schedules might make that a nuisance. That logistical hurdle might complicate meetings abroad after the pandemic subsides. And there’s also a potential new problem: If Chief Justice John Roberts opts out of presiding over the second impeachment trial of Donald Trump, Harris, as the Senate’s presiding officer, could occupy another visible, though vexing, spot in the chamber she just left. But the choice would be hers.