The paper shows that a non-legislative actor with a power to veto legislation can sell protection to lawmakers against opportunism in the plenary. So the veto power, especially the constructive kind that recognizes the issuer to make a counter-oer to the assembly (cf. Alem an and Schwartz 2006), turns presidents into eective brokers of legislative deals. The model is a form of Fighting Fire with Fire game (Heller 2001; Weingast 1992) where the president’s threat to retaliate amendments with further amendments disciplines potentially rebellious legislators; the president becomes the residual claimant, at the expense of defectors, in case the latter renege. The model also shows two limits of a president’s capacity to broker. Side payments may be required for a president who has too much ideological anity with opportunists, so as to prevent her from siding with them. And presidents with an absolute veto only are unable to enforce deals when the status quo is Pareto sub-optimal; those with a constructive veto can do it regardless of Pareto optimality. In future iterations, the paper will draw evidence from the Uruguayan legislative process.