The convention met in mid-May, after the Democrats had been forced to adjourn the 1860 Democratic National Convention in Charleston, South Carolina, without a nominee and had not yet re-convened in Baltimore, Maryland.
 With the Democrats in disarray and with a sweep of the Northern states possible, the Republicans were confident of victory.
 Senator William H. Seward of New York was generally expected to get the nomination.

Other candidates seeking the nomination at the convention included Lincoln, Governor of Ohio Salmon P. Chase, former U.S. Representative Edward Bates of Missouri, and U.S. Senator Simon Cameron of Pennsylvania.

As the convention developed, however, it became apparent that Seward, Chase, and Bates had each alienated factions of the Republican Party.
 Delegates were concerned that Seward was too closely identified with the radical wing of the party, and his moves toward the center had alienated the radicals.
 Chase, a former Democrat, was opposed by many of the former Whigs who had become Republicans, was thought to be too radical on slavery, had opposed tariffs wanted by Pennsylvania manufacturing interests, and critically, had opposition in his own delegation from Ohio.
Bates outlined his positions on extension of slavery into the territories and equal constitutional rights for all citizens, positions that alienated his supporters in the border states and southern conservatives.
German-Americans in the party opposed Bates because of his past association with the Know-Nothings.

It was essential to carry the West (what would today be considered the Middle West), and Lincoln was a prominent Westerner.
He had a national reputation from his debates and speeches, in which he eloquently opposed slavery while avoiding any of the radical positions that could alienate moderate voters.
He had the support of the Illinois and Indiana delegations before the convention, and was the strongest candidate other than Seward.

Nonetheless, Seward's prestige appeared likely to carry him to the nomination.

Lincoln was represented at the convention by his friends Leonard Swett, Ward Hill Lamon, and David Davis.
During the night of May 17–18, they worked frantically to win anti-Seward delegates for Lincoln.
They showed that Lincoln already had the most support after Seward, which persuaded some.
They also made a deal with Simon Cameron of Pennsylvania, who recognized that he had no chance of winning the nomination himself.
Cameron controlled the Pennsylvania delegation, and he offered to trade his support for the promise of a cabinet position for himself and control of Federal patronage in Pennsylvania.
Lincoln did not want to make any such deal; from Springfield, he telegraphed to Davis "I authorize no bargains and will be bound by none".
Despite this restriction, Davis reached an understanding with Cameron, which eventually led to Cameron's appointment as Secretary of War.

The next day (May 18), when voting for the nomination began, Seward led on the first ballot with Lincoln a distant second.
But on the second ballot, the Pennsylvania delegation switched to Lincoln, as well as some other delegates, putting him in a near-tie with Seward.
On the third ballot many additional delegates switched to Lincoln, and he won the party's nomination.
The convention met in mid-May, after the Democrats had been forced to adjourn the 1860 Democratic National Convention in Charleston, South Carolina, without a nominee and had not yet re-convened in Baltimore, Maryland.  With the Democrats in disarray and with a sweep of the Northern states possible, the Republicans were confident of victory.  Senator William H. Seward of New York was generally expected to get the nomination.
Other candidates seeking the nomination at the convention included Lincoln, Governor of Ohio Salmon P. Chase, former U.S. Representative Edward Bates of Missouri, and U.S. Senator Simon Cameron of Pennsylvania.
As the convention developed, however, it became apparent that Seward, Chase, and Bates had each alienated factions of the Republican Party.  Delegates were concerned that Seward was too closely identified with the radical wing of the party, and his moves toward the center had alienated the radicals.  Chase, a former Democrat, was opposed by many of the former Whigs who had become Republicans, was thought to be too radical on slavery, had opposed tariffs wanted by Pennsylvania manufacturing interests, and critically, had opposition in his own delegation from Ohio. Bates outlined his positions on extension of slavery into the territories and equal constitutional rights for all citizens, positions that alienated his supporters in the border states and southern conservatives. German-Americans in the party opposed Bates because of his past association with the Know-Nothings.
It was essential to carry the West (what would today be considered the Middle West), and Lincoln was a prominent Westerner. He had a national reputation from his debates and speeches, in which he eloquently opposed slavery while avoiding any of the radical positions that could alienate moderate voters. He had the support of the Illinois and Indiana delegations before the convention, and was the strongest candidate other than Seward.
Nonetheless, Seward's prestige appeared likely to carry him to the nomination.
Lincoln was represented at the convention by his friends Leonard Swett, Ward Hill Lamon, and David Davis. During the night of May 17–18, they worked frantically to win anti-Seward delegates for Lincoln. They showed that Lincoln already had the most support after Seward, which persuaded some. They also made a deal with Simon Cameron of Pennsylvania, who recognized that he had no chance of winning the nomination himself. Cameron controlled the Pennsylvania delegation, and he offered to trade his support for the promise of a cabinet position for himself and control of Federal patronage in Pennsylvania. Lincoln did not want to make any such deal; from Springfield, he telegraphed to Davis "I authorize no bargains and will be bound by none". Despite this restriction, Davis reached an understanding with Cameron, which eventually led to Cameron's appointment as Secretary of War.
The next day (May 18), when voting for the nomination began, Seward led on the first ballot with Lincoln a distant second. But on the second ballot, the Pennsylvania delegation switched to Lincoln, as well as some other delegates, putting him in a near-tie with Seward. On the third ballot many additional delegates switched to Lincoln, and he won the party's nomination.
1860 Republican National Convention