Republican politicians learned several things in the 2020 election’s aftermath. First, Trump’s failed campaign to overturn the results revealed a variety of mechanisms that may be exploited in future elections. Second, Republicans discovered that their base would not punish them for attempting to steal an election. To the contrary, they now know that efforts to overturn an election will be rewarded by Republican voters, activists, local and state parties, and many donors. The 2020 election was, in effect, a dress rehearsal for what might lie ahead. All evidence suggests that if the 2024 election is close, the Republicans will deploy constitutional hardball to challenge or overturn the results in various battleground states. Recent history and public-opinion polling tell us that the Republican activist base will enthusiastically support—indeed, demand—such tactics. The new state election laws will make that easier. Democratic strongholds in Republican-led swing states will be especially vulnerable. And if disputed state-level elections throw the election into the House of Representatives, a Republican-led House would likely hand the presidency to the Republican candidate (no matter who actually won the election). The American system has faced crises before—including the disputed elections in 1824, 1876, and 2000. Given the considerable authority that the Constitution grants to state legislatures, the processes of voting, vote counting, and even the selection of electors can easily be subverted for partisan ends. Electoral guardrails must therefore be hardened through federal legislation prior to the 2024 election.