Fillmore's support of the Compromise of 1850 may have been
wrong but it was hardly unimportant or uninteresting. Arguably it delayed the coming of the ACW by a decade. There certainly have been presidents less consequential than Fillmore--at least if Daniel Webster was right in saying that "if General Taylor had lived we should have had civil war."
https://books.google.com/books?id=FbUBAAAAMAAJ&pg=PA231 Some historians have claimed that Taylor, though opposed to the "Omnibus," would have signed the individual Compromise bills. However, there is a question of whether the bills would have passed in the first place without active pressure of the type Fillmore exerted. As I wrote here a few years ago:
"Of course, saying that Taylor would not have vetoed the Compromise does not necessarily mean that it would have passed in the first place had he still been president. Positive aid, not just a willingness not to veto, was if not absolutely necessary, at least helpful, and here Fillmore was certainly more useful than Taylor could have been. As Smith notes, Fillmore, having served as Congressman and Vice-President, was better acquainted personally with members of Congress, was more tactful, understood the workings of the system better, etc. The mere fact that he was known as an enemy of Seward's made some Southerners more friendly to the compromise, and he apparently did use personal relations and make a few patronage promises when the compromise was in its final stages. But Smith thinks that by then pro-compromise sentiment was so strong in most states (South Carolina of course being an exception) that passage was practically assured...
"I should add that Michael Holt (in *The Rise and Fall of the American Whig Party* puts more emphasis than Smith on Fillmore's role in getting the Compromise passed. The key vote, according to Holt, was the passage of the so-called "Little Omnibus" by 107-99. (Some of the preliminary votes were even closer.) Critical for its passage was the support of a number of Northern Whigs who had previously opposed any organization of new territories without the Wilmot Proviso. Holt thinks that while they may have been seriously worried about saving the Union, they were also influenced by the use of patronage by Fillmore and his Secretary of State, Webster... Holt's analysis can be found on pp. 539-543 of *The Rise and Fall of the American Whig Party.*
http://books.google.com/books?id=5aGyVFn3VnMC&pg=PA539