Baldasaro's grandfather served as mayor of Cambridge, Massachusetts for four terms, beginning in 1971. Baldasaro served in the U.S. Marine Corps for 22 years.
According to the Guardian, Baldasaro is "known as one of the most conservative—and controversial" members of the New Hampshire's 400-member House of Representatives. Baldasaro led the fight against same-sex marriage in New Hampshire. As of 2016, Baldasaro was serving his fifth term in the House.
In the 2012 Republican presidential primaries, Baldasaro supported Texas Governor Rick Perry. At a Republican primary presidential debate in 2011, the audience booed and jeered a gay Marine who had submitted a debate question about the "don't ask, don't tell" policy. When asked about the incident, Baldasaro said that he was "disgusted" by the Marine and said: "I thought the audience, when they booed the marine, I thought it was great." Baldasaro, who was criticized for the remarks by the Nashua Telegraph, defended his comments in the media, stating that it is against Department of Defense regulations to wear a PT uniform at a partisan event.
Baldasaro considered running for the United States Senate in the 2014 election but did not enter the race.
In late December 2015, in response to a Facebook post made by Democratic State Representative Amanda Bouldin's supporting breastfeeding in public and opposing a New Hampshire bill that would criminalize the exposure of women's nipples or breasts in public, Baldasaro wrote on his Facebook page, "Amanda, no disrespect, but your nipple would be the last one I would want to see. You want to turn our family beaches into a pervert show." Baldasaro refused to apologize or retract his remarks. The incident prompted Republican House speaker Shawn Jasper to ask state Representatives "to act with dignity, to act with respect" in his remarks the following month at the opening of the 2016 legislative session.
Baldasaro is an advisor to Donald Trump, the Republican nominee for president in the 2016 election, and appears regularly with him at campaign events. Baldasaro is the co-chairman of the Trump campaign's national veterans coalition.
Baldasaro was a delegate at the 2016 Republican National Convention. At the convention, Baldasaro called for the execution of Democratic presidential candidate Hillary Clinton, accusing her of treason and saying she should be "put in the firing line and shot”. Baldasaro declined to apologize for his remark and then repeated it. New Hampshire Republican Senator Kelly Ayotte responded that “This kind of rhetoric is totally irresponsible, it has no place in our society, and violence should never be encouraged against anyone.” The Secret Service investigated Baldasaro over the remarks.