What he said is true.

Definition of resentment

a feeling of indignant displeasure or persistent ill will at something regarded as a wrong, insult, or injury

Anyone who is sane and rational and has watched the president on the campaign trail this week, campaigning for other Republicans, could not honestly say he, Trump, the leader of the Republican party, “isn’t capitalizing on resentment” to get Republican candidates elected or reelected in order to retain control of Congress.

Barack Obama spoke truth to power there in Illinois.