Democratic presidential candidate Hillary Clinton promised a dinnertime crowd of Suffolk Democrats Monday night she’d support federal investment in roads and railways to “make sure it’s possible to enjoy living and working on Long Island.”

The Suffolk County Democratic Committee’s spring fundraising dinner was the final stop of Clinton’s day on the Long Island campaign trail. Earlier Monday, she took part in a panel discussion on gun violence and also met with Newsday’s editorial board.

Monday night, she told the 850 people attending the dinner at Villa Lombardi’s in Holbrook that “it’s important we have suburban policy. . . . We don’t pay enough attention to what smart growth looks like and I’m going to make sure that we do.”

Clinton joked about the area’s traffic woes, saying she welcomed any opportunity to visit Long Island, but “I don’t want to make the traffic even worse.”

The former secretary of state looked to galvanize support among Suffolk Democrats before the state’s April 19 primary, in which she faces a challenge from Sen. Bernie Sanders (I-Vt.). Clinton asked the crowd to show up at the polls to generate “a big positive New York election.”

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Clinton touted her time as New York’s former U.S. senator, reminding the crowd she worked to protect the Long Island Sound, keep the 106th Air National Guard Rescue Wing at Gabreski Airport and secure benefits for 9/11 first responders.

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Suffolk Democrats raised more than $500,000 with the record number of attendees, Suffolk Democratic Chairman Rich Schaffer told the crowd. Tickets were $300 each.

About 25 people stood across the street from the event, most holding anti-Clinton signs, but others said they came to catch a glimpse of the Democratic front-runner.

Earlier Monday, Clinton held a panel discussion on reducing gun violence, telling a somber audience in Port Washington that as president she would stand up to the powerful gun lobby.

Clinton shared the stage with activists who told stories of losing their loved ones to gun violence.

“Let’s figure out what we’re going to do to save lives,” Clinton said at Port Washington’s Landmark on Main Street.

She touted her “common-sense agenda” to close loopholes that expand gun ownership, saying that too many times she has “looked into the eyes and held the hand of people who ask, ‘Why? How can we let this happen?’ ”

Gun control legislation is one of the few issues on which Clinton is decidedly left of Sanders, whose rural state has lax firearms laws.

A host of the event, Rep. Steve Israel (D-Huntington), pointed out the ideological rift in his introduction.

“There’s a critical contrast in this campaign on the issue of gun violence,” he said. “Hillary Clinton supports the Brady Bill; her opponent voted against it five times.”

The legislation, signed into law in the 1990s by Clinton’s husband, former President Bill Clinton, in part mandates federal background checks on those who buy firearms.

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On stage with Clinton was Erica Lafferty, daughter of slain Sandy Hook Elementary School Principal Dawn Hochsprung.

Lafferty said gun violence victims are sometimes seen as “nothing but a number,” but she wants to keep Hochsprung’s memory alive as a passionate educator.

Clinton has criticized Sanders as an ally of the National Rifle Association. Clinton also has slammed him for a Senate vote he cast in 2005 to protect gun manufacturers from prosecution in gun-related crimes.

Sanders told the New York Daily News editorial board this month that he opposes permitting families of gun violence victims to sue the firearms industry.

He has defended his views on gun rights, saying firearm ownership in rural states like his is largely associated with hunting, and he understands gun violence is a separate issue altogether in urban America.

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Clinton said Monday that Sanders’ argument that he represents a gun-friendly state holds little water because the “highest per capita number of guns that end up committing crimes in New York come from Vermont.”

With David M. Schwartz