The fight over Merrick Garland, President Obama’s nominee to fill the Supreme Court vacancy cased by the death of Associate Justice Antonin Scalia, has been pushed almost entirely out of the news by the ongoing presidential primary battles. But, while it may be out of sight to most people, there’s striking evidence in a new NBC-Wall Street Journal poll that Democrats are winning the message war over Garland.

This slide, from Democratic pollster Peter Hart’s analysis of the data, tells that story:

Initially, public opinion was deeply divided — largely along partisan lines, with Democrats on the side of a confirmation vote held before the end of the year and Republicans content with leaving the seat open until a new president took office. In March, opinion was moving toward the “vote this year” option. In the poll released Monday night, a majority now believe the Senate should hold a confirmation vote on Garland this year.

The next obvious question is: Where is the change coming from? And, thankfully, Hart offers that up, too.

Fascinating, no? The gains made by the “vote this year” crowd come, at least in part, by changing opinions of Republicans (plus 8 percent since March) and conservatives (plus 10 percent). Even Republican primary voters have grown 5 percentage points more amenable to the idea of holding a vote on Garland this year.

Sen. Susan Collins (R-Maine) bucksSenate Republican leaders April 5, praising President Obama's U.S. Supreme Court nominee. (Reuters)

Now, there's a BIG difference between saying that you’d prefer that the Senate hold a confirmation vote on Garland this year and actually voting with that issue in mind on Nov. 8. The classic example of this is campaign finance reform. Large majorities of people, when polled, say that there should be less money in politics. And yet, it is an actual voting issue for a much, much smaller group. It’s why campaigns that put money in politics at their center — Democrats in the last two midterms, for example — almost never win.

Simply because public opinion is moving in Democrats’ direction on a Garland vote doesn't mean that Senate Republicans will cave anytime soon. Why? Because they know that the segment of their party that might actually vote on how they handle this Supreme Court nomination still doesn’t want a vote to happen.

But the movement in the polls to the Democratic view on Garland is unmistakable and will probably encourage Democrats and their affiliated groups to push even harder on GOP senators up this fall in swing states — and there are lots of them — to move off their current positions on Garland.