Donald Trump has a man problem. No, not what you think — this is not about sexist remarks or boorish behavior. Donald Trump, whose candidacy is conventionally thought to rest on the support of working class white men, is not attracting nearly as much enthusiasm from them as Mitt Romney did four years ago. Given his poll deficit to Hillary Clinton, if Trump cannot fire up his base of support, Republicans are headed for big losses in November.

The Reuters/Ipsos poll asks respondents to rank themselves on a scale of 1-10 of how likely they are to vote. The average score on this scale can be used as a (very) rough forecast for turnout. However, even more useful, the question can be used to compare the relative enthusiasm of different portions of the electorate at different points in time. The graphic below shows the voter enthusiasm as forecasted turnout in June 2016 and June 2012 by gender.

Using the Reuters/Ipsos poll turnout estimate, overall enthusiasm is down slightly this year, from 53.3 percent to 51.8 percent and enthusiasm is equally down among men and women. However, when we dig deeper into supporters of Clinton and Trump, the picture changes. Below is the same information with Trump and Clinton voters broken out from the whole population (compared to Romney and Barack Obama supporters in 2012).

Relative to voter enthusiasm levels in 2012, Clinton shows only a minimal decline compared to Obama, split evenly between male and female supporters. Trump, on the other hand, sees a pronounced fall-off compared to Romney, particularly among men. In 2012, male voters were Romney’s main block of support. Trump, despite a reputation for firing up his male base, is underperforming Romney’s mark by almost eight points.

Given that Republicans usually rely on very strong turnout from their base to overcome Democrats’ population advantage, this finding is problematic for Trump. As things currently stand, Trump trails in the polls and will not be able to count on turnout to give him a boost. These data indicates that Trump needs to adjust his strategy to better mobilize Republicans, but what should he do? One more chart can help shed light on that.

This shows Trump vs. Romney supporters by gender and self-identified conservatism. Now Trump’s problem is very apparent. Among male supporters who lean conservative, Trump trails Romney’s mark by more than 20 points. This indicates that there are a lot of moderate voters who are inclined to pull the lever for Trump, but are not happy about it. Unless Trump can figure out how better to appeal to these moderate voters, he will continue to have a hard time catching up to Clinton in the race for the White House.