President-elect Trump recently announced the nomination of his former National Economic Council member Gail Slater as assistant attorney general for antitrust at the Department of Justice and chose current Federal Trade Commission commissioner Andrew Ferguson to head that agency.  Trump’s antitrust enforcers’ priorities will include prosecuting market power abuse by “big tech,” supporting consumers and “little tech,” and enforcing “clear rules that facilitate, rather than stifle, the ingenuity of our greatest companies.” To do that, they must learn from the mistakes of their aggressive, outgoing counterparts. Though both presidents share a wariness of tech giants, Trump’s vision departs from the Biden-administration experiment which tried blocking an unprecedented range of business practices and mergers based on speculative (rather than probable) harms.  Policy goals such as income redistribution, labor and environmentalism have been well outside the traditional economic-competition lane. Instead, Biden’s Justice Department and Federal Trade Commission view big businesses with market power as inherently bad, even if they benefit consumers. Trump’s team must pick its battles more carefully. Antitrust agencies have limited resources and should prioritize cases they’re likely to win based on both legal precedent and plausible theories of harm to competition, innovation, and American consumers. The Biden Justice Department and Federal Trade Commission 2023 joint merger guidelines failed to provide clarity to businesses about which mergers would attract prosecution. It also disregarded decades of precedent. This drove businesses to abandon deals that were likely to stand, foster competition and benefit consumers — all out of fear of multiyear, multimillion-dollar litigation. FTC and Justice Department leadership touted this as a success. Exorbitant FTC litigation contributed to cancer-test developer GRAIL and blood-test platform provider Illumina abandoning their planned merger, even though a federal judge had found that the agency failed to consider the firms’ offer to work with other platforms to resolve anti-competitive concerns. This likely resulted in significant delays in the rollout of lifesaving medical technology. The FTC offered other “impermissibly speculative” theories of harm and was rebuffed in blocking tech deals such as Meta’s acquisition of fitness app Within and Microsoft's acquisition of game developer Blizzard/Activision. Courts found that it disregarded competitive synergies that were likely to benefit consumers and increase competition against rival firms like Sony. The agencies have had more recent success contesting mergers between head-to-head competitors. The FTC blocked fashion giant Tapestry’s $8.5 billion acquisition of smaller rival Capri after showing it would reduce competition. It successfully blocked Novant Health’s $320 million purchase of two North Carolina hospitals after arguing they would lead to higher prices and less competition locally. In fact, hospital mergers have traditionally been a source of government antitrust wins on patient-welfare grounds. The current FTC faces criticism for failing to adequately police these while expending resources on weaker, headline-grabbing tech cases. This isn’t to say agencies can’t pursue novel cases where harm to competition and innovation is likely. The Biden Justice Department successfully blocked the merger of Penguin and Simon & Schuster after arguing the resulting publishing giant could offer authors smaller advances, discouraging quality writing and leaving consumers worse-off. The second Trump FTC and the Justice Department should withdraw the flawed guidelines and publish new ones recognizing that mergers can be pro-competitive and reflect the market’s latest legal and technological developments.  For instance, even in declining to dismiss the FTC’s case against Meta’s acquisitions of Instagram and Whatsapp, the DC District Court criticized the agency for ignoring competition from LinkedIn, X, Tiktok and YouTube, a serious hindrance to its case. Similarly, the Justice Department’s case against Visa defines an unrealistically narrow market of debit-card networks, ignoring the growing competitive threat of fintech networks, like the Clearing House’s Real Time Payments which already process billions of transactions yearly.  Trump’s administration should change tack on inherited cases like this, much as it will probably do with the Justice Department proposal to force Google to divest its search engine and Chrome browser. Trump acknowledges that this would destroy the value of Google’s tools to consumers, including “little tech” firms reliant on Google services. Finally, U.S. competition enforcers should restore America’s global leadership. Prior administrations promoted both consumer-focused antitrust and freer international markets. Biden’s agencies have departed from this even as foreign competition agencies unashamedly favor their own industries and extract wealth from U.S. firms. The House Committee on Oversight and Accountability is investigating the FTC for cooperating with European antitrust enforcers to prevent the Amazon-iRobot merger. Allegedly, the FTC’s strategy was to assist foreign governments when they challenged the merger since the legal threshold to do so overseas is lower. Opaque moves do not benefit global competition or U.S. prosperity. Don’t expect a lassiez-faire antitrust approach from Trump, whose first administration brought high-profile cases and investigations against many of the same corporate and tech giants. But by carefully selecting cases and strategy, his second administration can achieve a pragmatic, pro-innovation and pro-consumer antitrust policy. Satya Marar is a postgraduate fellow in Innovation, Competition and Governance at the Mercatus Center at George Mason University.