Trump has reiterated his "complete endorsement" for the candidate four times on Twitter, but on the eve of Election Day he took another unprecedented step.
Trump made his endorsement live on a conference call with Jacobs and several others. Although it was billed as a "tele-town hall," no questions were taken.
However the president made it clear, this call was unusual.
"I don't do these often but it's an honor to do it for Chris," Trump said. "He's a fantastic guy who has been a very, very successful state senator."
He spoke after an introduction from Jacobs for a little more than seven minutes. The president expounded on many of the key themes of his endorsement tweets, telling voters Jacobs is a strong candidate for veterans, those in favor of secure borders, and gun rights.
"He would just fight as strong as you could fight because he loves the area, loves the region," Trump said. "So do I by the way. I did very well there (in 2016)."
He pointed out that he was supporting Jacobs in both the primary and the special and reminded people to vote in both. He did not name the candidate's Republican opponents but he did have some choice words for the Democratic candidate Nate McMurray.
He said McMurray would among other things, take away guns, open borders, and support sanctuary cities.
"Nate McMurray, I did a lot of research through my people," Trump said. "He's a radical liberal controlled by crazy Nancy Pelosi — and she is crazy — and the do-nothing Democrats."
McMurray said the last-minute town hall means the president and Jacobs are "scared." He said Trump is trying to "steal a win."
"TRUMP just attacked me in a town hall for Jacobs, saying he did a lot of 'research on me.' Then he spewed a river of lies," McMurray tweeted. "He also praised @NHLBruins. I thought @DelawareNorth had nothing to do with @JacobsNY27."
The Democrat appears to have surmised that the Jacobs "family member" Trump said he called to ask about Chris early on was Jeremy Jacobs, the billionaire owner of the Boston Bruins and the Delaware North hospitality company and the candidate's uncle.
"This should be a message to all of WNY. Don't be fooled." McMurray said in a statement. "Trump says he's for the people but he is standing with billionaires and losing to us. Who are we? Volunteers. Friends. Family. Not afraid to say to him, or anyone else, we want a country that is fair, kind, good."
While Trump headlined the conference call, Congresswoman Elise Stefanik and Republican National Committee Chairwoman Ronna McDaniel also offered their support. McDaniel stressed the importance of GOP voters going to the polls and getting their friends and family to do the same.
"We know that Nate McMurray will be just another AOC (NY Rep. Alexandria Ocasio-Cortez) in the House. He is a radical liberal and we have to win back this seat and make sure that we put Chris Jacobs in Congress," she said.
New York's 27th Congressional District includes eight counties in Western New York and is arguably the reddest in the state. Jacobs concluded that McMurray doesn't align with the values of the district's voters and "actually mocks them."