Answer:
It means that though Abraham Lincoln may be the President of the country, his opposition of the slavery system is not something he can just simply take into consideration. His duty to the nation precedes his personal opinions.
Step-by-step explanation:
The above excerpt is from the letter written by Abraham Lincoln to Albert G. Hodges, editor of the newspaper Frankfurt, Kentucky, Commonwealth. President Lincoln had been an avid supporter of the emancipation of slaves.
In the letter, he wrote that though he is personally against the slavery system, being the President doesn't ensure that he should abolish it. He might be the President of the country, with absolute power, but he had taken an oath to protect and preserve the interest of all the citizens. And he knows there are a lot of people who still wants the slavery system. So, he can't just ignore these people's interest and act like a dictator. His first duty is to the nation and the constitution, which he had sworn an oath to do so.