I often hear laments that, despite all the other things going wrong for the GOP, Trump himself has an unshakable base of support that will ultimately save him and his party.
This is a myth. Yes, Trump has a strong base of support, but it is not extraordinary and is subject to attrition among voters who have questions about him, his behavior and/or his policies. Trump has not invented an new form of politics where he is invulnerable to voter defection.
First point, his approval rating among Republicans. This is high but hardly unprecedented by historical standards. According to Politifact:
"The most recent publicly available data from Gallup’s weekly tracking poll at the time of Trump’s tweet showed him with 85 percent approval from Republicans.
So how does that 85 percent rating compare with his Republican predecessors? We looked at Gallup historical data for Republican presidents going back to Eisenhower. We looked for the closest polling data for July 29 of their second year in office (the day of Trump’s claim). We used the equivalent period after the inauguration of Gerald Ford, who unlike the others was not sworn in on Jan. 20.
So...not only did George W. Bush have a higher approval rating among Republicans, but so did Dwight Eisenhower and, arguably, George H.W. Bush.
Two other points of comparison make Trump’s achievement less impressive.
One is to compare Trump’s highest approval rating of his tenure so far — 90 percent as recently as mid-July — to the record-high rating for his predecessors through July 29 of their second year in office.
By this measure, Trump actually ties for the second-worst of any post-World War II Republican president, surpassing only Ford.
Another approach is to compare each president on the highest approval rating of their tenure. (Trump has only been in office for a year and a half, but he opened the door to this analysis by claiming the "highest poll numbers in the history of the Republican Party.")
Once again, by this measure, Trump fares the second worst of any post-war Republican president, only surpassing Ford.
By historical standards, Trump has had "solid, but not extraordinary in-party approval," said Kathleen Joyce Weldon, director of data operations and communications at the Roper Center for Public Opinion Research at Cornell University."
Second point: Support for Trump is relatively weak among large and important groups of Republicans. According to a study by political scientists Peter K. Enns, Jonathon P. Schuldt and Adrienne Scott:
"During the first two weeks of July, we fielded a nationally representative survey of 1,379 likely voters. Conducted online and on the phone by the National Opinion Research Center, we included only respondents who reported a high likelihood of voting in this year’s midterms. The survey was funded by Cornell’s Center for the Study of Inequality.
In our survey, Trump’s approval rating was 85 percent among Republicans. That’s consistent with other polls. On the surface, the president’s support among his fellow Republicans is overwhelming.
But the key to our analysis was to divide Republicans into three groups: those who say they identify strongly with the Republican Party; those who identify as Republicans but not strongly; and those who call themselves independents but say they lean toward the Republican Party. These distinctions, often obscured in media coverage, are important because research shows that the strength of a voter’s partisan identity has an important effect on their political attitudes.
Among strong Republicans, Trump’s overall approval rating is 93 percent, with 78 percent “strongly” approving of the president. The problem for Trump, however, is that these voters make up less than half of the Republican electorate — and 18 percent of likely voters.
Among the larger number of Republicans who identify less strongly with their party, Trump is much less popular. For example, Trump’s overall approval rating among not-so-strong Republicans is 72 percent, with 38 percent saying they strongly approve. Thirty-four percent say they only “somewhat” approve of Trump. Those numbers are similar among independent-leaning Republicans."
Third point: Not everyone who voted for Trump is very happy with him. That matters. Nate Cohn on newly-released Pew data:
"There has been little change in President Trump’s approval rating in the last 18 months, and so it’s often assumed that nothing can erode his base of support. The Pew data suggests it’s not so simple.
Yes, nearly half of Mr. Trump’s voters have exceptionally warm views toward him: 45 percent rated their feeling toward him as a 90 or higher out of 100, a figure that is virtually unchanged since his election. But a meaningful number of his voters had reservations about him in November 2016, and even more Trump voters held a neutral or negative view of him in March.
Over all, 18 percent of Mr. Trump’s voters gave him a rating of 50 or less, on a scale of 0 (coldest) to 100 (warmest), up from 13 percent in November 2016.
It is worth noting that the November 2016 Pew survey was taken after Mr. Trump won the presidency, at the height of his post-election honeymoon. But even when you consider the slightly lower ratings voters gave him in the months before the election, the big picture is the same: A modest number of Mr. Trump’s voters didn’t like him that much then, and don’t like him much now.
Women, and especially college-educated women, are the likeliest Trump voters to have serious reservations about him in 2018: A striking 14 percent of the college-educated women who voted for him hold a very cold impression of him, up from just 1 percent in November 2016."
So don't believe the hype. Trump's support is plenty shakable. And it's being shaken.