He was; but I have a source to how just how, in terms of popularity, Lincoln stood with the electorate in general.:
Lincoln, Abraham—and popularity as president. Sometimes a myth will arise as the result of overly enthusiastic attempts at debunking. One such is the statement sometimes made that Lincoln was not really a popular president. But in fact he was. Certainly he had enemies; a wartime president can scarcely hope to be free from attacks arising out of the public frustrations and despair which are a part of wartime. And the opposition press in Lincoln’s day, an era of journalistic vituperation scarcely equaled before or since, was sometimes so extraordinarily vicious in its comments that it is not always easy to remember they reflected only the opinions of editors, not the public. It should also be remembered that Horace Greeley, the most influential journalist in Lincoln’s time, was responsible for many of the attacks on Lincoln—possibly because Greeley had backed another candidate, Seward, for the 1860 nomination, possibly because Greeley apparently had the kind of temperament that seizes upon causes rather than issues. (A blistering attack on Lincoln written by Greeley was scheduled for appearance when the news of Lincoln’s assassination reached the New York Tribune, Greeley’s paper. It was killed in Greeley’s absence by the managing editor, who explained to Greeley that the *Tribune * would have been wrecked by a mob if the editorial had been run—and that the *Tribune * would have deserved it.)
Lincoln, was not, it is true, elected by a “majority”; his share of the popular vote was 39 percent. But he was running against not one, but three other candidates. [His name was not even on the ballot in the states that eventually seceded. –d.m.] And, in fact, Lincoln’s margin over Douglas, his leading opponent, was more than 500,000. When he was reelected in 1864, his lead over McClellan was about the same—some half a million. The population of those states which did not secede was about 22 million during Lincoln’s tenure. Lincoln’s popular majority in 1864, thus, represents a margin equivalent to about 4.5 million today . Whether or not the term “landslide,” applied by some historians, is applicable, it is nonetheless true that Lincoln’s victory over McClellan in 1864 was greater in equivalent terms than Franklin Delano Roosevelt’s over Thomas E. Dewey in 1944. And this time Lincoln captured over 55 percent of the popular vote.
When Lincoln was assassinated, even those newspapers that had been the most bitter in their comments while he lived poured forth a torrent of adulation. In the words of Robert S. Harper (Lincoln and the Press, 1951) “It was no longer possible to determine the politics of a newspaper by what it said about Lincoln.” Enemies Lincoln certainly had; no public figure can hope to escape them. But by the only standard that determines popularity on a statistical basis rather than a historian’s opinion—the election returns—Lincoln was indeed a popular president.
From The Dictionary of Misinformation by Tom Burnam, 1975, pp.141-142. (Bolding and bracketing mine)