Why, then, did what appeared to be a constitutional structure evenly divided between the two branches so quickly tip in favor of the executive? The legacy of the colonial and revolutionary eras played a key role, as did the increasing professionalization of U.S. foreign policy. So, too, did the national security threat posed by the wars of the French Revolution. Perhaps most important was the intimate link between international issues and the first party system, which caused most contentious foreign policy questions to be debated along partisan rather than institutional lines. Not surprisingly, therefore, the presidency of John Adams, characterized by a closely divided Congress and contentious relations between the two branches, broke relatively little new ground in terms of altering the legislative-executive relationship, at least in the long term. The last Federalist president, for example, made sure to obtain congressional approval for the technically undeclared Quasi-War with France.
The War of 1812 transformed both the international and domestic environment, and in the process it altered the nature of the legislative-executive relationship. In the international arena, the Treaty of Ghent, followed closely by the Rush-Bagot agreement demilitarizing the Great Lakes and the Adams-Onís Treaty obtaining Spanish Florida, ended any credible European threat to the country's survival. Domestically, the unity between the executive branch and a majority of the legislature did not survive the 1820s schism among the Jeffersonian Republicans. In this new context, members of Congress began using foreign policy issues to obtain political advantage over the executive. One example came in 1817 and 1818, when Henry Clay attempted to force diplomatic recognition of the Spanish-American republics through direct congressional action. Clay believed that the United States, as a state founded in revolution itself, should assist other colonies attempting to win their freedom. But the speaker of the House also realized his initiative would embarrass his chief rival for the presidency, Secretary of State John Quincy Adams, and thus might work to his political benefit. Adams proved the more skillful politician, however, a trait he demonstrated again six years later when he discerned the electoral merit in a unilateral U.S. declaration opposing European recolonization in the hemisphere (the Monroe Doctrine). Partisan concerns also appeared prominently in the first major foreign policy fight between the two branches during Adams's presidency, the resolution to obtain congressional backing of his effort to send U.S. delegates to the 1826 Panama Congress. A Senate filibuster delayed the appropriations necessary to fund the delegates' mission.
These skirmishes set the stage for the period between 1844 and 1860, which featured the most clear-cut intersection of partisan, institutional, and ideological battles matching Congress against the president. By 1860, the legislature's power on foreign policy reached, arguably, its highest point in American history. Few would have predicted this outcome when the expansionist James Polk captured the presidency in 1844. Without congressional sanction, Polk ordered U.S. troops into territory disputed between the United States and Mexico, triggering a battle between armed forces of the two nations. When Congress finally did consider a declaration of war, with fighting already under way, the administration used procedural tactics to ram the measure through both houses. Polk's conduct thus exposed him to the charge of usurping legislative prerogatives, reopening dormant debates about executive authority in foreign affairs. Meanwhile, the introduction of the 1846 Wilmot Proviso (which called for forbidding slavery in any newly acquired territories) eradicated the line between international and domestic matters by clearly linking slavery and expansion. At one pole of congressional opinion, abolitionists in the House aggressively made the case against expansionism. Led by John Quincy Adams (Whig-Massachusetts) and Joshua Giddings (Whig-Ohio), they transferred their opposition to slavery at home to an attack on imperialism abroad and used the war to indict the slave power's dominance of the nation's political structures. In the process, figures like Adams and Giddings showed how voices shut out of executive branch deliberations could make themselves heard through congressional action.
Partisan gridlock accompanied this ideological polarization, blocking any hope for Polk to retain the backing that he enjoyed in 1846, when only fourteen members of the House and no senators voted against the war declaration. The changing context of foreign policy issues splintered his electoral coalition, diluting support for the president's bid to annex all of Mexico. With Polk complaining privately about Congress having paralyzed his diplomacy, his term ended with Latin American policy immobilized by the sectionalization of manifest destiny, institutional conflict between the legislative and executive branches, intense partisan attacks, and sharp disagreement between proslavery expansionists and abolitionist anti-imperialists.
In the end, a penchant for secrecy, bypassing Congress, and allowing his domestic base to atrophy undermined Polk's freedom of action. His successors, the Whig presidents Zachary Taylor and Millard Fillmore, discovered that a foreign policy focused on limiting U.S. expansionism through treaties with other imperial powers lacked appeal in a Congress increasingly polarized over expansionism. The first attempt of the Whigs in this regard was the Clayton-Bulwer Treaty of 1850, in which the United States and England agreed that neither would unilaterally construct a trans-isthmian canal; the party's second was the Tripartite Treaty of 1852, in which the United States, England, and France agreed to respect the status quo in Cuba. Furious Senate objections, from not only southerners but northern senators such as Henry Wilson, forced Secretary of State John Clayton to interpret his 1850 handiwork restrictively; similar Senate opposition prompted President Fillmore to shelve the Tripartite Treaty altogether.
In this environment, implementing a bold international agenda could not occur without stable congressional support. In meeting this requirement, the final chief executive of the period, James Buchanan, displayed a good deal of originality. Buchanan believed that, given the domestic tumult of the preceding decade, foreign powers would take him seriously only if he could prove that, in contrast to Polk, Taylor, Fillmore, and Pierce, Congress would not block his actions. The new president therefore attempted a variety of approaches to augment his position—at the legislature's expense. In 1858 he requested from Congress a resolution granting him discretionary authority to wage war against Paraguay, a procedure he later proposed expanding to all Latin American diplomatic issues. A year later, he sought to advance his most important goal—annexing Cuba—by urging Congress to appropriate $30 million to initiate the process. He (and his Senate critics) expected that once having spent the money, the upper chamber would not reject any future treaty bringing Cuba into the Union.
But in these and other initiatives Buchanan found himself consistently rebuffed by Senate Republicans. An ideological diverse coalition led by Republican Jacob Collamer of Vermont inflicted on the president an embarrassing defeat during initial consideration of the Paraguayan resolution. Collamer again played a leading role in attacks against the $30 million bill, and now Republicans with a higher national profile, such as New York's William Seward and New Hampshire's John Hale, joined them. This fierce opposition to the $30 million bill, for instance, attracted notice as far away as Madrid. William Preston, the minister sent by the administration to begin negotiations for the purchase of Cuba, was left to lament: "The character of the debate in Congress… has gone very far to revive the hopes of the Spaniards that they will be able to retain the island, and that our discord, and the distraction of party, will render the United States powerless in any struggle." The four decades following the Treaty of Ghent thus witnessed a legislature much more willing to launch (and much more effective in sustaining) ideological and legislative challenges to executive supremacy.
After 1860, however, the changing international and domestic environment caused congressional Republicans to reconsider their earlier conviction that Congress should reign supreme in U.S. foreign policy. During the Civil War, severe divisions over both military and Latin American issues split apart the GOP caucus. As Wisconsin Republican James Doolittle joked of his New Hampshire colleague John Hale, the upper chamber's most outspoken anti-imperialist, a "long habit of continued denunciation against the Administration or the party in power for fifteen or twenty years in succession has had some effect on the habits of his mind." In addition, with their party dominating the presidency throughout the period, Republicans grew less enamored (except during Andrew Johnson's presidency) with philosophical defenses of an active congressional role in foreign policy. That several leading members of the party struggled to use the congressional committee system to oversee the conduct of the Civil War undoubtedly reinforced this disinclination.
Despite these developments, Congress retained more than enough power to block aggressive international initiatives. The willingness of Gilded Age chief executives to uphold tradition and negotiate substantial agreements with foreign powers as treaties reinforced Congress's influence. The failure of the three most ambitious of these treaties—U.S. Grant's scheme to annex the Dominican Republic in 1870, the 1884 effort to establish a U.S. protectorate over Nicaragua, and Benjamin Harrison's gambit to annex Hawaii in 1892—prompted future secretary of state John Hay to compare a treaty entering the Senate with a bull going into the arena, in that neither would depart alive. Hay's comment testified to the strength of the ideologically awkward but politically potent coalition of the remaining Republican anti-imperialists, such as Carl Schurz and Charles Sumner, and most of the body's Democrats. Once again, ideological extremes exerted a disproportionate influence in Congress. Senate Democrats cared little about anti-imperialism, but they believed that increased executive authority in international affairs would establish a precedent that presidents could later use to unilaterally advance the cause of civil rights. Congress even proved capable from time to time of acting in a more positive fashion, as in 1888, when majorities in both houses passed a resolution demanding that Grover Cleveland's administration initiate a conference of Western Hemisphere nations to address trade and other economic issues.