CNN  — 

Midterm elections – like the one coming up in 2018 – are all about turning out base voters. Why? History tells us that only the most stalwart partisans turn out when the presidential race isn’t on the ballot. So if your side wants to pick up House and Senate seats in a non-presidential election, you need to find ways to excite its most committed members.

Which is where the Republican tax plan approved by the Senate last week comes in. And the fact that, according to a new CBS poll, lots more people hate the plan than love it.

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Just 16% of people in the poll said they “strongly” approved of the GOP tax plan. That number pales in comparison to the 40% who said they “strongly” disapprove of it.

A similar question – “Which best describes how you would feel if the Republican tax plan was signed into law?” – produced equally concerning results for Republicans. Just 8% said they would be “excited” by the new tax law while 22% said they would be “angry.” (Another 28% said they would be “satisfied” and 31% said they would be “disappointed.”)

Dig into the numbers and the direness for Republicans becomes more apparent. While 46% of Republicans strongly approve of the tax plan, 71% of Democrats strongly disapprove.

Ditto the “angry” versus “excited” breakdown. Just 19% of Republicans said they were excited about the prospect of the tax bill becoming law as compared to 39% of Democrats who said they were angry.

What those numbers suggest is that the Republican tax bill is a major motivator for Democratic base voters and far less of one for the GOP base. Meaning that the tax bill looks far more likely to drive Democrats to the polls to show their anger and disapproval than it is to push Republicans to vote next November in support of it.

The base enthusiasm problem surrounding the tax bill is indicative of a broader enthusiasm gap between the two party bases. Democrats, at the moment, are extremely motivated to go to the ballot box and send a message – a negative one – to President Donald Trump. Republicans are far less enthused to turn out to show support for Trump.

In Virginia’s 2017 election, Democrats comprised 41% of the overall electorate as compared to just 30% for Republicans, according to exit polling. Almost half of the electorate (47%) said they strongly disapproved of Trump, and Democratic nominee Ralph Northam won 95% of those voters.

If Republicans can’t close that enthusiasm gap, they are in for a very rough 2018 election. And, at least at first glance, their much-touted tax cut plan makes their passion problem worse, not better.