If an incumbent president is seeking to run again, who will his party likely nominate?

The party will most likely, unless something really major happened, nominate the President as the their candidate. The president in the U.S. as stated in the 22 Amendment can't be in office longer then two terms, each lasting four years. This is based on the precedent made by George Washington, who himself served two terms.

In my honest opinion , i’d say franklin d roosevelt was a president that impacted our nation , i say this because fdr is voted among top three best us presidents and he was the longest serving president by 3 terms , usually presidents only supposed to have two terms increments of 4 years , equivalent to 8 years total before election time. and he established the fdic , through the 1933 banking act and he established the us , social security system , during his presidency, and established a national minimum wage , through the fair labor standards act , fdr led the allied coalition to victory in wwii and he played a major role in the creation of the united nations.