Brazilian presidents’ ability to govern vary significantly. Some presidents are more successful in getting their legislative initiatives passed by the national congress, but others do not enjoy the same level of success, sometimes despite their large legislative coalitions. Some are even impeached by the national congress. What explains the variations in the ability of the presidents to achieve legislative success? This presentation examines legislative activism and obstruction in a coalitional presidential system by highlighting the roles of political negotiation within the governing coalition and ideological proximity between the president and parties in the governing coalition. My study shows that heterogeneous governing coalitions composed of many political parties make coalition management more difficult, leading to greater scrutiny of executive proposals in committees and more votes on the same bill, causing legislative gridlock and delay. Moreover, the ideological gap between the president and his or her coalition increases legislative attempts to kill executive proposals both procedurally and substantively. The centrality of the ideological location of the president within the coalition and also vis-à-vis the median party in the lower house has tremendous implications not only for presidents’ legislative success but also for their survival.