The most important factor determining the fortunes of the Know-Nothings in Pennsylvania was popular anti-party sentiment. Although the Know-Nothing order's original raison d'être was nativism, Pennsylvania Americans rose to political prominence in the state through their oft-repeated argument that the established parties were no longer representative of the views of the electorate. To be sure, reformist appeals had been the staple of third and emerging political parties prior to the rise of the Know-Nothings. What aided the Know-Nothings' reformist agenda, however, was the emergence or re-emergence of a number of issues that cut across traditional party lines or the established parties had difficulty staking a position on. The reticence and equivocation displayed by the Whig and Democratic parties on such issues as slavery extension, temperance and the sale of the state's public works, provided strong evidence of the Know-Nothing claim that the old parties cared more for their own interests. Pennsylvania voters, therefore, convinced of the sagacity of the Know-Nothings' anti-party appeals, deserted the established political parties and lent their allegiances to the one organisation that seemingly had staked out popularly representative positions on the issues that most concerned them- the Know-Nothings.
While the Know-Nothings wasted no opportunity to speak on issues that the established parties hoped to ignore, the order's position on these issues, for the most part, constituted little more than an attack on the established parties for their failure to address the concerns of the electorate. Indeed, when the order was forced to confront an issue, Know-Nothings often found themselves working at cross-purposes. The most serious example of this occurred with the Nebraska bill and the controversy over the further extension of slavery. Having vested their political fortunes so heavily in their anti-party agenda, Pennsylvania Know-Nothings, moreover, were especially susceptible from the appearance of any deviancy from this agenda. Another crucial element of the Know-Nothings' anti-party based program was their claim that the established parties were motivated solely by the desire to further their own interests and concerns. As a force for political reform, the order's promise ran, voters could be assured that the Know-Nothings' only political motivation was to represent the popular will. During their failed attempt to elect a new U.S. senator, however, the back-room manoeuvrings and political infighting that the Know-Nothings had pointed to as manifestations of self-interested motivations, characterised the order's behaviour in the first test of their devotion to their anti-party agenda. Consequently, just as antiparty ism was the most significant factor in the Know-Nothings' phenomenal rise in Pennsylvania, so too was it responsible for the order's equally precipitous demise.