Ron Johnson is no stranger to being a squeaky wheel inside the Senate GOP. Now he’s asking for trillions of dollars worth of grease.

The frequently cantankerous Wisconsin senator is pushing his fellow Republicans to deliver huge spending cuts as part of their party-line domestic policy bill — and vowing to block President Donald Trump’s top legislative priority if his demands, which are shared by a small cadre of fiscal hawks, aren’t met.

As the megabill moves through the House, Johnson’s increasingly vocal warnings are an early indicator for Senate GOP leaders and the White House that they’ve got major headaches awaiting across the Capitol. Senate Republicans can only afford three defections on the expected party-line vote.

“I think there’s enough of us that would say, ‘No, that’s not adequate,’” Johnson said in an interview where he described his insistence on returning the federal government to “pre-pandemic” level of spending.

The math issue that creates for Republicans is stark: The House GOP is struggling to hit $1.5 trillion in spending cuts, while Johnson and his allies want to go much, much further. Returning to the level of federal expenditures that predates multiple rounds of pandemic stimulus, a major infrastructure bill and the Democrats’ own domestic-policy megabill would, by Johnson’s own estimation, require more than $6 trillion in cuts.

GOP leaders might laugh off such an audacious demand if Johnson didn’t have a history of getting what he wants.

The last time Republicans wrote a party-line tax bill, in 2017, he vowed to oppose the package as he pushed for better treatment of so-called “pass-through” businesses, which comprise most privately held companies. Formerly an executive for a Oshkosh plastics manufacturer, Johnson argued that the bill needed to benefit smaller businesses as much as it would benefit large corporations that were in line to get a major rate cut.

His hardball tactics paid off big time: Republicans ultimately included a new 20 percent deduction rate for pass-through business income, an estimated $414 billion line item in the $1.5 trillion Tax Cuts and Jobs Act.

Now, with key TCJA provisions expiring, he’s asking for roughly 10 times the fiscal impact, and his colleagues have learned not to brush him off.

“He’s as serious as a heart attack,” said Sen. Kevin Cramer (R-N.D.), who credited Johnson for driving a hard bargain back in 2017. But he also suggested any Republican would have a hard time standing in the way of the party’s top legislative priority: “Sometimes when confronted with a binary choice people compromise a little more.”

While Johnson is setting his sights in the multi-trillion-dollar range, he’s hinting that a substantially smaller settlement might be possible: He suggested in an interview that lawmakers could enshrine a chunk of the overall cuts in the pending GOP bill while also setting up a bicameral commission to find the rest by going “line-by-line” through the federal budget.

“Elon Musk is showing us how to do this right?” he said. “You expose, ‘Whoa, what are we doing spending money on that?’” he said.

But Johnson hasn’t yet found buy-in for that idea from colleagues who have been burned by one too many deficit-cutting commissions that ultimately sputtered. The response he’s gotten, he said, is “we don’t have time to do it.”

“Well, okay then, I don’t have the support for the bill,” Johnson said.

GOP leaders believe they have a strategy to navigate around Johnson, which goes back to their decision to bundle together wildly disparate parts of their domestic agenda — tax cuts, border security upgrades, deportation funding, energy incentives, Pentagon plus-ups and more.

That, they believe, will make it too big to fail. But Johnson had a less optimistic metaphor as he gaggled with reporters on Wednesday, saying it instead “might be like the Titanic and may be going down.”

Johnson has instead repeatedly floated breaking up the bill into two or three or more pieces — something that would force GOP leaders in both chambers to abandon a hard-fought budget blueprint and go back to the drawing board.

He’s no stranger to playing the skunk-at-the-garden-party role inside the Senate GOP. Abandoned by national party committees during his 2016 Senate run, he has long felt unusually free to chart his own path and sometimes critique his own party’s leadership. He’s used his leadership posts on the Senate Homeland Security and Governmental Affairs Committee to pursue matters top GOP leaders would otherwise just leave alone — most recently conspiracy theories related to the 9/11 terror attacks.

Johnson’s not the only potential Senate Republican holdout GOP leaders are dealing with on the “big, beautiful bill.” Sen. Rand Paul of Kentucky is all but guaranteed to be a “no” after opposing the budget blueprint. Several others are viewed as potential swing votes, including Republican Sens. Josh Hawley of Missouri, Lisa Murkowski of Alaska and Susan Collins of Maine.

Asked about the House bill, Murkowski quipped, “It’s not beautiful yet.”

Senators are expected to make changes to the House bill, if and when it comes over, meaning Johnson will have an opportunity to put his stamp on the legislation. He’s a member of the Finance Committee, which has broad jurisdiction over both taxes and health care, where the GOP is looking to reap most of the savings.

Senate Majority Leader John Thune, another Finance member who put a big stamp on the 2017 bill, said Republicans are looking to end up with spending cuts on the “north end” of the $1.5 trillion to $2 trillion range.

“We take all our members seriously,” Thune said about Johnson. “I know it’s a huge priority for him, which is why I’ve suggested all along that [the House] prioritize spending cuts in the package.”

Republicans, of course, are also betting that Trump can ultimately force the fiscal hawks, who are typically more MAGA-aligned than moderates like Collins and Murkowski, to stand down. That’s what happened earlier this year when the budget plan was teetering, and Johnson was invited with other fiscal hard-liners on the Budget Committee to meet with Trump at the White House.

Johnson was among them, and he, too, eventually fell in line.

Now, he says, he’s determined to make good on campaign promises to get the nation’s fiscal house in order that date back to his first run as a tea-party-influenced political outsider in 2010.

“I’m trying to lead,” he told reporters Wednesday, adding, “When I talk to Trump about it, he agrees with my approach.”