There is one point of inferiority in our system to yours which has been very little touched on, and that is the way in which the Presidential office tends to put a premium upon a man's keeping out of trouble rather than upon his accomplishing results. If a man has a very decided character, has a strongly accentuated career, it is normally the case of course that he makes ardent friends and bitter enemies; and unfortunately human nature is such that more enemies will leave their party because of enmity to its head than friends will come in from the opposite party because they think well of that same head. In consequence, the dark horse, the neutral-tinted individual, is very apt to win against the man of pronounced views and active life. The electorate is very apt to vote with its back to the future!
Roosevelt attempted to demonstrate his point with reference to his own electoral prospects.
In my own case, for instance, I believe that most of my policies have commanded the support of a great majority of my fellow-countrymen, but in each case I have made a certain number of determined foes. Thus, on Panama I had an overwhelming majority of the country with me; but whereas I am not at all sure that any Democrat will vote for me because of my attitude on Panama, there are a certain number of mugwumps who will undoubtedly vote against me because of it. So as regards Cuban reciprocity. The country backed me up in the matter, but there is not a Democrat who will vote for me because I got Cuban reciprocity, while there are not a few beet sugar men who will vote against me because of it. In the same way the country breathed freer, and felt as if a nightmare had been lifted, when I settled the anthracite coal strike; but the number of votes I shall gain thereby will be small indeed, while the interests to which I gave mortal offense will make their weight felt as of real moment. Thus I could go on indefinitely.
The fact that Roosevelt won the 1904 election in a landslide might disprove his premise. Historians would argue that he was wrong about Democrats, since many had been crossing over to vote Republican since the 1896 election, when Democratic nominee William Jennings Bryan's populism alienated many longtime partisans. In modern times, the concept of "Reagan Democrats" appears to belie Roosevelt's pessimism about crossover voting. But neither scenario quite matches the situation Roosevelt described. Democrats crossed over in 1896 to repudiate Bryan, and in 1980 to repudiate Jimmy Carter. On the other hand, both McKinley and Reagan were re-elected, Reagan by a larger margin than his first election. If Roosevelt was complaining that partisanship prevented many people from giving a leader the credit he presumably deserved, the 1984 election would seem to refute him more than any other.
Roosevelt made a larger point about the difficulty of building a trans-partisan coalition that arguably remains more relevant today. His main complaint to Trevelyan was that the system appeared to prevent him from making up with gains from across party lines for the alienation of people within his own party ranks. In his own mind, Roosevelt had won a hard fight against entrenched interests within his own party to advance his own agenda. Eight years later, as an insurgent ex-President, he would lose a similar fight and abandon the Republicans to form the Progressive party -- and then, despite most likely still being the most popular man in America, he lost the 1912 presidential election. He might well have blamed that outcome not only on Democrats refusing to abandon their party to support him, but from the more obvious refusal of many Republicans to do likewise. Near the moment of his greatest political triumph, he already perceived to some extent that parties were bigger than men, even powerful men like himself, and had interests potentially different from those of the men appointed as their standard bearers. He thought the British system superior because there, he believed, the Prime Minister was the undisputed leader of his party and less vulnerable to interest groups within the party. In the U.S., the interests seemed to dominate parties, and the parties themselves were interests that could overrule individuals of vision and action. However overwhelming Roosevelt's 1904 victory appeared, in his own mind he had simply beaten the odds -- and he couldn't depend on doing that every time.