Lina Khan’s rise to chair of the Federal Trade Commission has been celebrated by Silicon Valley’s critics as the dawn of a new age of tougher antitrust enforcement.

She was sworn into office with one of the most ambitious visions of any chair at the agency, following years of high-profile proposals to dismantle large tech companies’ power that she spelled out both in her academic writing and in her guiding of a congressional investigation into Big Tech’s power.

But her promise is about to collide with the reality of the FTC, an agency more than 100 years old that has come under fire in recent years for failing to police privacy and competition abuses.

“She wants to take a car that she thinks has been driving at about five miles per hour and make it go 250,” said William Kovacic, a former chairman of the agency.

Khan is entering the agency at a critical moment, with pressure mounting from members of both political parties to rein in tech companies. That’s resulting in greater scrutiny of the FTC’s track record.

Khan inherits a key antitrust lawsuit against Facebook, which seeks to break the social network up over allegations that it copied, acquired and killed its rivals. The lawsuit is being watched as a test of Washington’s ability to check Silicon Valley’s power amid a broader debate about reforming tech regulations.

She’ll also be running an agency that lawmakers and experts for years have warned is under-resourced and lacking deep technical expertise, at a time when companies are growing ever more powerful and wealthy and building bigger lobbying forces in Washington.

And there will be immediate pressure for Khan to do more: Anti-monopoly groups have called on the agency to pursue similar competition complaints against other tech giants, including the e-commerce titan Amazon. (Amazon CEO Jeff Bezos owns The Washington Post.)

But those efforts will confront a U.S. judicial system that for decades has held a fairly narrow view of what constitutes an antitrust harm, which could be a major hurdle to achieving Khan’s sweeping vision of competition enforcement.

“She’s got some things that can be done under existing law, but nothing like what she wants to get done,” said Herbert Hovenkamp, an antitrust professor at the University of Pennsylvania’s law school.

Amid this backdrop, Khan is likely to face immediate, intense pressure from anti-monopoly groups that have been calling for greater antitrust enforcement. Their expectations are incredibly high.

“The constituency that wanted her appointment to take place has expectations that are not merely stratospheric, they are out of this world,” Kovacic said. “She hasn’t even stepped foot in her office yet, and they are speaking as if she’s traveled to Mars.”

Breaking up major tech companies or bringing about other big changes to those companies’ operations may hinge on Congress overhauling competition laws. A bipartisan group of lawmakers last week introduced a series of bills that would outlaw many of the allegedly anticompetitive tactics that tech companies used to solidify their dominance. But it’s unclear whether they’ll all pass a bitterly divided Congress, as some Republicans raise concerns about them.

It seems likely the agency will see its funding grow under Khan, especially after the Senate passed legislation that would overhaul merger filing fees to provide more financing to antitrust enforcers. House lawmakers have introduced a similar proposal, which is less controversial than some of the other tech competition bills.

There remain many uncertainties about Khan’s tenure: She is coming into the FTC with a 3-2 Democratic majority, but it’s unclear how long that will last. Rohit Chopra (D) is awaiting his confirmation to the Consumer Financial Protection Bureau. When he leaves, it could be difficult for President Biden to build the bipartisan support needed to install another commissioner.

And nearly five months into his term, Biden has yet to announce who will run the Justice Department’s antitrust division. Experts say the federal government’s success in taking on the tech giants hinges on those agencies working together.

Former FTC officials and antitrust lawyers say one immediate area where Khan could create change is in personnel at the agency. Her bold vision could excite people and be a draw for recruiting new technologists and legal minds. And she’ll have broad authority over who leads bureaus within the agency, allowing her to set the agenda.

“That’s where there’s real opportunity to reinvigorate the FTC and its priorities,” said Ashkan Soltani, a former chief technologist at the agency.