The first of two parts

Donald Trump was successful as a presidential candidate in part because he carried the Independent vote. In recent years, Democrats have enjoyed roughly a five-percentage-point lead over Republicans in terms of partisan identification, which means that to win, Republican presidential candidates need to do well with Independents. The 2016 exit polls showed Trump beating Hillary Clinton approximately 46 percent-42 percent among Independents, but this figure was probably on the low side: The post-election edition YouGov re-contact survey (where 5,000 respondents were interviewed 16 times over the course of the election) had Trump winning 54 percent of Independents.

Many surveys focus on Trump’s strength among his base, as well as on Republican support for him and Democratic opposition to him. In this analysis, we focus on Independents’ reactions to Trump over the first six months of his presidency. Taking two surveys per month from public YouGov polling, we examine partisan and Independent approval of the president, in addition to their opinions on his handling of the economy and foreign policy. The measure used is the difference between approval and disapproval (net approval); thus, if 65 percent disapprove and 35 percent approve, the score is -30 percent approval. Figure 1 shows Trump’s overall approval/disapproval score by Democrat, Republican and Independent.

The results show little variation among partisans, with the possible exception of Republicans who are slightly less supportive than they were at the beginning of Trump’s administration. Nevertheless, net approval for the president among Republicans remains at +60 percent.

Democrats started out anti-Trump and, over the entire time series, have at least a net -60 point approval number. This dislike is unsurprising, given the country’s entrenched polarization: Republicans were similarly down on Barack Obama in the first six months of his presidency, also approving by -60 percent. In any event, members of both parties have been remarkably stable in their assessment of Trump: Democrats against, Republicans for.

Independents, on the other hand, have moved from a net positive number in January to a steadily increasing net negative approval rating. In June, the gap against Trump was in double digits and by early August it was over 20 points: 30 percent approve and 51 percent disapprove in the latest YouGov poll. It is not surprising that a polarizing figure like Trump draws the ire of Democrats and the support of his party; his present problem is that he has lost support among the Independents who ultimately gave him the presidency.

We also looked at Trump’s approval/disapproval numbers for his handling of foreign affairs (Figure 2) and the economy (Figure 3).

As was the case in overall approval, Democrats disapprove of his work in the area of foreign affairs, while Republicans generally approve of it. Again, it is the Independents who change most notably, moving from net approval to double-digit disapproval of the president’s handling of foreign affairs.

The bright spot for the president is approval for his handling of the economy. Republicans have given him high marks in this area from January 30 through early August, even as Democrats have steadily expressed disapproval in this regard.

Significantly, Independents – who began with a slightly positive approval number on Trump’s handling of the economy – have held constant at roughly 50 percent approval/50 percent disapproval. Thus, on probably the most important single issue to U.S voters, Trump is outperforming his overall approval rating among Independents.

One obvious implication here is that when the economy slows, as it inevitably will, Trump’s support among Independents will likely cool along with it.

The overall story for the first seven months of the Trump era is that the president has maintained his co-partisans’ approval, never had the Democrats’ approval, and has lost some support among Independents. Carefully monitoring future developments among Independents is critical – as long as there are fewer Republicans than Democrats in this country, Independents will remain absolutely essential to Republican electoral success. At the moment, they are less supportive of Trump than they were in January -- and may be poised to become even less supportive if the nation’s economic fortunes take a hit.

Tomorrow: An appetite for impeachment?

David Brady is a professor of political science at Stanford University and the Davies Family Senior Fellow at the Hoover Institution.