Wisconsin Sen. Ron Johnson, one of the most vulnerable GOP incumbents  in 2016, is closing in on his competitor, according to one poll.  

The Marquette University Law School survey  of 1,405 registered voters from March 24-28 showed the gap between Johnson and his Democratic challenger, former Sen. Russ Feingold, narrowing from 12 points to 5 in February.  

Most of Marquette’s polls from the past year have had Johnson behind by double digits, except for an August survey, where he was also down by 5 points.  

The gap in this latest poll narrows even further when looking only at likely voters who say they will vote in November: 48 percent support Feingold, while 45 percent back Johnson.  

The poll, conducted over landlines and cell phones, has a margin of error of plus or minus 3.3 percent for the full sample.  

This month’s survey is only one poll — hardly evidence of a consistently tightening race — but for Johnson’s campaign it underscores the message that this is a competitive election.  

“This is going to be a close race all the way to November and everyone knows it,” Johnson campaign spokesman Brian Reisinger said in a statement.  

With heightened attention on his state five days before Wisconsin’s presidential primary April 5, it’s especially good news for the campaign that the latest public poll, which will be getting more eyeballs because of the presidential ballot questions, shows a tighter race.  

Feingold has consistently outraised Johnson. Earlier this month, the Chamber of Commerce endorsed Johnson , but it’s unclear whether that support will come with funds. Johnson spent nearly $9 million on his 2010 campaign but has said he won’t be pouring the same personal resources into his election  this year. Meanwhile, his campaign has been eager to paint Feingold as a hypocrite on campaign finance issues.  

While the most vulnerable senator — Illinois’s Republican Sen. Mark S. Kirk — is going moderate ahead of November, Johnson is not. Kirk met with President Barack Obama’s Supreme Court nominee Merrick Garland Tuesday , but Johnson — who is widely seen as the second most vulnerable  — is sticking with the overwhelming Republican election-year position of not granting Garland a hearing or a vote.  

In an interview with CNN earlier this week, Johnson said he thought that position would help him with his November re-election. He also suggested that the new voters turning out for Donald Trump would help down-ballot candidates like him. While most vulnerable Republicans are trying to distance themselves from Trump, Johnson didn’t rule out campaigning with him.

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