State Rep. Geoff Diehl is setting up a federal fundraising account in his first official move toward challenging U.S. Sen. Elizabeth Warren, offering an early gauge of how much anti-Warren money could flow into the race from around the country.

Diehl, a conservative Whitman Republican who’s publicly weighed a Senate bid for months, plans to open a campaign account and file a statement of candidacy with the Federal Election Commission tomorrow, he told the Herald.

The four-term state lawmaker is aiming to raise “six figures” by the close of the next FEC reporting in June, and said how much money he raises will dictate a move from a self-described “exploratory” prelude to an official campaign. But it’s a major step forward to framing both an expected GOP primary and challenge to Warren, who’s already said she’ll seek re-election in 2018.

“My take is, this is going to be a lot of what happened with Scott Brown … where money just poured in from across the country,” said Steve Aylward, a Diehl political ally and state committeeman who worked closely with Diehl on their statewide campaign to repeal a hike to the gas tax in 2014.

Brown, a state senator from 2010 to 2013, rode a wave of national anxiety over the impending Obamacare bill to a U.S. Senate seat — which, more than two years later, he lost to Warren in the costliest U.S. Senate race in history.

“Elizabeth Warren, around the country, is seen as Trump’s major nemesis,” Aylward said. “I think a lot of money is going to come in from across the country.”

A prolific fundraiser, Warren already had $4.8 million in her account to close 2016, with more expected to flow in once filings from the most recent fundraising quarter, which ended last week, are made public later this month.

Diehl pointed to the gas-tax repeal, where the committee was out-raised 30-to-1, as evidence he can build a base of support beyond money in the bank. He’s also previously framed any challenge of Warren as a race of interest to President Donald Trump, who views her as a “major obstacle,” Diehl has said.

“This is a big step not just for me, but other Republicans in the state,” said Diehl, who chaired Trump’s Massachusetts campaign. “This will give us the additional indicator of how we will do in fundraising and continuing to grow the support base to win a race like this.”

Diehl, however, could face a motivated Democratic base in Massachusetts eager to push back on all things Trump.

“The Trump election has really energized the grassroots in Massachusetts in a way I haven’t seen in a while,” said Doug Rubin, who advised Warren during her 2012 campaign. “I think if the Republican playbook in this election is to bring a lot of outside money and Donald Trump support to bear on this election, I’m not sure that’s a winning strategy.”