CNN will host the final three Republican candidates at a live town hall in Milwaukee from 8-11 p.m. ET Tuesday.

Story highlights

Sen. Ron Johnson of Wisconsin is among the most vulnerable Republicans in 2016

He's ready to counter-attack against Democrats over the Supreme Court and Donald Trump

Waukesha, Wisconsin CNN  — 

Democrats are planning a two-front war to take back the Senate: tying Republican senators to Donald Trump and castigating them for refusing to give even scant consideration to President Barack Obama’s Supreme Court nominee.

Sen. Ron Johnson is perfectly fine with that.

The Wisconsin Republican, who rode a tea party wave to office in 2010, is viewed as one of the two most vulnerable members of his party in a Senate that Democrats hope to retake in November.

He’s taking a far more aggressive line against the Supreme Court nominee, Merrick Garland, than any other vulnerable senator facing re-election. In the latest sign that Republicans are unlikely to defect from their party leadership’s opposition, Johnson is arguing that Obama’s pick is so far out of the mainstream, including on the Second Amendment, that he doesn’t deserve a hearing, much less a vote.

Johnson, 60, said in an interview with CNN that his demand to let the next president decide the Supreme Court nominee will be a boon for him in his closely contested race with former Democratic Sen. Russ Feingold. And if the Supreme Court doesn’t move voters, he thinks Trump will.

Support for SCOTUS hearings remains strong, CNN/ORC poll finds

After Johnson toured a metal factory here in the Milwaukee suburbs, he said that Trump as the GOP nominee would benefit Republicans down-ticket by turning out voters who may otherwise choose to stay home – particularly in northern Wisconsin and in rural corners of the state. He seems to have no problem campaigning with Trump, either.

“Stump with Trump?” he quipped when asked if he’d appear on the campaign trail alongside Republican front-runner. “Just because it rhymes: It’d be the Ronald (and) the Donald.”

Johnson added: “Certainly as I travel the state extensively, I hear a lot of support because what Donald Trump is saying resonates with an awful lot of people when it comes to the incompetence of Washington, D.C.”

The comments reflect how the two parties are making fundamentally different calculations about how voters will respond in the battle for control of the Senate, where the GOP currently holds a 54-46 majority.

Nightcap: The latest news and political buzz from CNN Politics | Sign up

On the Supreme Court, most Republicans are betting that the issue will essentially be a wash: It will energize their base and core Democratic voters equally, while dividing independents. Unlike Democrats, Republicans are confident that the issue won’t interest most middle-of-the-road voters, meaning GOP senators have little incentive to back off their position to deny Garland a hearing.

On Trump, Republican senators are uncertain how his nomination would play politically. Increasingly, GOP senators are preparing to distance themselves from the businessman’s more divisive rhetoric – as Johnson did in repudiating Trump’s plan to ban Muslims from entering the country – but they don’t want to abandon the real estate mogul because they’ll need his voters to come to the polls in the fall.

“From what I’ve heard, Trump is running very strong up in the Northwest (part of the state)… that should also help me a bit too,” Johnson said.

Supreme pressure?

Johnson is widely viewed as one of the two most vulnerable Republicans in the country – the other being Sen. Mark Kirk in Illinois, who will meet with Garland on Tuesday. In Wisconsin, Johnson is facing a well-known foe in Feingold, the long-time senator of 18 years who lost by 5 points in 2010 to Johnson – then a political neophyte running against an established name in Wisconsin politics.

Feingold is trying to do something that hasn’t been accomplished anywhere since 1934 – win back a seat lost in the previous six-year election cycle. Yet, Johnson is battling headwinds of his own: Wisconsin hasn’t backed a Republican for the White House since 1984, meaning he will have to mount a particularly strong campaign to win during a presidential election year.

In the year of Trump, both Feingold and Johnson are battling for the mantle of the true outsider.

Feingold, a former member of the Senate Judiciary Committee who supported George W. Bush’s pick, John Roberts, to become the chief justice, said that Johnson’s refusal to even consider Garland shows how he walks in lockstep with his party’s partisan agenda.

“Sen. Johnson is engaging in pure obstructionism and, in my view, showing no respect for the President or the Constitution,” Feingold said in an interview. “What the Republican majority is setting into motion here is a process that could destroy the United States Supreme Court permanently.”

Moran becomes third GOP senator to call for Garland confirmation hearings

To ratchet up the pressure, organized about 40 liberal activists to demand action last week in Milwaukee city hall. A plane circled around, carrying the banner, “Sen. Johnson: Do Your Job. #FillTheSeat.”

“We think the Republicans are gambling that the people won’t care about this and that the issue will go away,” said Paul Geenem, the head of the Milwaukee chapter of the Obama-backed Organizing for Action. “And we’re going to try to make sure that the issue doesn’t go away.”

A new CNN-ORC poll gives Democrats some ammunition, with 64% of voters nationally saying Garland should at least be given confirmation hearings and 52% arguing he should be confirmed for a lifetime seat on the high court.

Who is Merrick Garland?

Yet what’s disheartening to Democrats is there’s little evidence to show that the issue will galvanize voters this fall. The Supreme Court routinely ranks below other top-tier issues such as the economy and national security. And a Marquette University poll from last month shows why Johnson is refusing to acquiesce: 65 percent of his supporters want him to hold firm and deny a Supreme Court nominee confirmation until 2017.

“Our supporters do not want to see the Supreme Court flipped from five conservatives – to four liberal judicial activists,” Johnson said in the interview. “This judge is pretty – he’s got a proven record of being pretty hostile to Second Amendment rights to keep and bear arms. That’s kind of important in the state of Wisconsin. So I think in general if anything it will probably be to my benefit” to deny hearings.

Garland supporters have said that the criticism over his Second Amendment position is unfair, arguing he’d bring a moderate view of the issue to the court.

A different approach

Most Republicans seem to side with Johnson, but Kirk does not. The vulnerable Illinois Republican recently called on his colleagues to “man up” and at least vote up-or-down on the nomination.

“If I have to vote, I’ll vote. I don’t have a problem with that. But again I recognize reality that’s not going to happen,” Johnson said. “The fairest and most democratic process in terms of Supreme Court nominees is let the American people have a voice.”

For Republicans, defending the Senate means stemming their losses in a daunting environment where they are trying to hold 24 seats, compared to 10 for the Democrats. And Democrats believe if Trump continues to offend women and minority voters, it will be the death-knell for Senate Republicans.

How $67 million failed to stop Trump

Yet, Republicans in Washington say they are heartened that the GOP senators in Illinois, Ohio and North Carolina have all racked up more votes than the party’s top presidential candidates during their states’ primaries.

Johnson, almost certainly, will have to do the same.

But in a year in which polls show Congress’ approval rating once again at rock-bottom, Johnson believes that by labeling Feingold as a “career politician” who is “desperate to get back into a position of power,” the GOP senator can portray himself as the true outsider in the race. That is similar to Trump’s narrative.

“I think people realize I’m truly an outsider,” said Johnson, who ran a plastics manufacturing company before running for office. “You don’t get further outside than I do going into Washington, D.C.”

CNN’s Brad Parks contributed to this report