Potomac businessman David Blair pauses after the Democratic candidates for county executive in Montgomery County debate November 15, 2017. (Katherine Frey/The Washington Post)

Potomac businessman David Blair spent a record $5.4 million on his unsuccessful campaign for Montgomery County executive, channeling his own money in a way never before seen for a local political race in the county.

Blair’s latest campaign finance report, filed Tuesday, shows that he loaned his campaign $2,518,000 between June 11 and Aug. 9, on top of previous loans of $2.6 million and his own contributions of $301,640. He finished a close second in a six-way primary, losing to at-large council member Marc Elrich by 77 votes.

Blair, who was criticized for his spending during the campaign by several of his Democratic primary rivals, was traveling Wednesday and unavailable for comment.

This year was the first in which Montgomery’s public campaign financing system — designed, in part, to reduce the influence of big money in politics — was available to candidates.

Three of the six Democratic executive candidates opted to use the system, including Elrich. He was the only one to receive enough small contributions to qualify for the $750,000 maximum in matching funds for the primary.

Blair’s spending is reminiscent of the financial effort made by another Potomac businessman, Total Wine & More co-founder David Trone, in his two congressional races. In 2016, Trone lost the 8th District Democratic primary after spending $13 million of his own money. He spent more than $10 million this year to win the 6th District nomination.

But big money isn’t typically the norm for local seats in Montgomery, said former District 3 council member and public-financing architect Phil Andrews (D), who called Blair’s spending “unusual.”

Former at-large county council member Steve Silverman, also a Democrat, previously held the record for money spent in a county executive race, after he raised $2.7 million in his unsuccessful 2006 bid against Isiah Leggett (D).

“I think it’s just reflective of the fact you had a multimillionaire in the race that could spend his own money,” Silverman said of Blair’s spending. “I don’t think it sets a new standard.”