While most of the people who voted for Trump on Nov. 8 said they would back him again, the erosion of support within his winning coalition of older, disaffected, mostly white voters poses a potential challenge for the president. Trump, who won the White House with the slimmest of margins, needs every last supporter behind him to push his agenda through a divided Congress and potentially win a second term in 2020.

The poll surveyed voters who had told Reuters/Ipsos on Election Day how they had cast their ballots. While other surveys have measured varying levels of disillusionment among Trump supporters, the Reuters/Ipsos poll shows how many would go as far as changing the way they voted. The survey was carried out first in May and then again in July.

[Click here to see an expanded view of the data: tmsnrt.rs/2vkyX7C]

In the July survey, 12 percent of respondents said they would not vote for Trump "if the 2016 presidential election were held today" - 7 percent said they “don’t know” what they would do, and the remaining 5 percent would either support one of the other 2016 presidential candidates or not vote.

Eighty-eight percent said they would vote for Trump again, a slight improvement over the May figure of 82 percent. Taken together, the polls suggest that Trump’s standing with his base has improved slightly over the past few months despite his Republican Party’s repeated failures to overhaul the healthcare system and multiple congressional and federal investigations into his campaign’s ties to Russia.

To be sure, most presidents lose support among core supporters the longer they are in the White House. According to the Gallup polling service, former President Barack Obama saw his popularity dip among Democrats and minority voters, though it did not come until later in his first term. But Obama, who won the Electoral College with greater margins than Trump, was not as reliant on retaining his core supporters.