從事憲政工程應該考慮當地的歷史丶社會條件丶政治文化以及未來的展望，尤其是在政體從一專制轉換爲民主的過程中，更應是如此。近來，有爲數不少的國家採取所謂的半總統制，與內閣制或總統制是大不相同的。憲政工程師應該避開以下兩個障礙：（1)行政與立法部門間的僵局，（2）由一人擅權的獨裁。爲解決僵局的問題，設計出強勢的總統，似乎是其答案。但是過度強勢的總統，尤其如果其又具個人魅力，可能導致其擁有絕對權力－拿破崙及凱撒是歷史的敎訓。總統的實力決定於權力在憲法上如何界定。權力的結合，尤其是形成或解組內閣以及解散國會的權力，是其實力的來源。政黨體制是決定總統是否能依其意志行使權力的因素。在一半總統制的政府，可能發生國會多數黨支持的總理與總統屬不同黨的共治情況。對總統權力的限制，首要應是指，不將由總理及國會可以執行較好的權力，給予總統。不過，如果有必要賦予總統緊急處分權，應要求總理的副署，或者得由國會否決。幾乎在所有半總統制的國家，其總統在外交及國防上皆負重要的角色，如果是的話，其應該具有某一程度的有關人事權。

Constitutional engineering has to consider the history, societal con­ditions, political culture, and the intended prospects, especially for a political system that is in the process of transformation from autocracy to democracy. Recently quite a few countries have resorted to a regime termed semi-presidentialism, differing from parliamentarism and presidentialism (see the article by Ernst Veser). It is the task of constitutional engineers to avoid two obstacles: (1) deadlock between the legislative and the executive branches, and (2) dictatorship through seizure of power by one person. To overcome dead­ locks, the institutionalization of a "strong" president seems to be the answer. But too strong a president, especially if he is a charismatic per­sonality, could be tempted to seize the absolute power—bonapartism or cesarism are the historical warnings. Strength depends on how powers are defined in the constitution. It emerges from the combination of powers, the most important of which are the formation and the dismissal of the government as well as the dissolution of parliament.The party system will determine if the presi­dent is able to wield such powers according to his wishes. In a semi-presidential regime cohabitation may occur: parliamentary majority of a party, backing the prime minister, in opposition to the "president's party". Curtailing presidential prerogatives means, in the first place, not to extend them to those fields that can better be executed by the govern­ment of the prime-minister (and parliament). If, however, it seems neces­sary to endow the president with emergency powers they can be made dependent on the countersignature of the prime minister or liable to rejection by parliament. Nearly all "semi-presidents" are considered to have an important role in foreign affairs and in defense, and if so, they must be able to have a say in the staffing.