President Lincoln was almost assassinated on April 14, 1865 at the Ford's Theatre, but the assassin was stopped by John Frederick Parker, who was killed instantly. The Ford's Theatre would be renamed as the John Frederick Parker's Theatre in his honor, given that he sacrificed his life to save the president. President Lincoln would seek re-election in 1868 and won the election with only 53.3% of the popular vote despite his popularity. Lincoln did think of running again in 1872, but sick of the infighting between linerals, moderates and radicals in the GOP, he ultimately decided to retire, even though the GOP would not lose a presidential election until 1884.
After Teddy Roosevelt's failed attempt to seek a fourth term, the 20th Amendment would be passed to limit the presidency to not more than three four-year terms to honor the socalled "Lincoln tradition". Would it even exist without the "Lincoln tradition"? Or maybe, Teddy Roosevelt would not have been a war hero, and would not have been elected President in TTL?
Lincoln was also the first president to open up a presidential library, just seven months before his death in 1890. Would we have presidential libraries anyway?
Today, Lincoln is considered one of the greatest presidents in our history given not only his contributions to national unity, emancipation and the first civil rights legislation; but his excellent political skills. However, had the plot succeeded, Andrew Johnson would have become President. He was a Southerner, would he simply follow Lincoln's reconciliation approach when dealing with the South given his background? As well, would he try to push for the Civil Rights Act of 1870 that was already widely criticized for being too weak at the time by radicals; or would Johnson simply roll back on civil rights?
OOC: POD: In TTL, poor John Frederick Parker decided to slip away to the tavern later. He was not really protecting the president. He was about to leave when John Wilkes Booth came, and Booth had to shoot him to death first. He would ironically be seen as a symbol of loyalty in TTL.