About 11 days later, Portman wrote back saying he cares about addressing gun violence and insisted that he did vote in favor of stronger background checks for gun buyers.
"[T]he Grassley amendment I supported would have reauthorized and improved the National Instant Criminal Background Check System," Portman wrote to Shulman.
The substitute GOP bill Portman voted for -- which was also rejected -- would not close any loopholes for buyers to dodge background checks. Instead it would enhance the amount of mental health reporting into the existing database. It would restore gun rights for recovered mentally ill people, those who are in a psychiatric hospital for observation, and those who commit themselves voluntarily. The National Rifle Association supported the bill but gun control advocates say it would make it easier for dangerous people to obtain guns.
Shulman, an assistant professor of history at Case Western Reserve University in Cleveland, noted that Portman's explanation may appear to someone unfamiliar with the policy details as support for expanding background checks, even though he voted against the policy.
"He's absolutely obfuscating his position," Shulman told TPM by phone on Tuesday afternoon. "I think it's completely misleading. And it seems designed to mislead."
Portman joins the ranks of fellow GOP Sens. Kelly Ayotte (NH) and Jeff Flake (AZ). They hold the same stance as Portman but have also claimed to support stronger background checks while weathering the political storm for voting against the popular policy. The gun lobby opposed the expanded measure and promised to target senators who voted for it.
Although he claimed to support background checks, Portman admitted in his letter to Shulman that he opposed the main background check legislation, arguing that while it would have "expanded background checks for most private sales and private transfers of guns," it would have "done nothing to stop the Newtown tragedy."
Shulman said he didn't vote for Portman in 2010 and wouldn't consider voting for him again unless he changes his position on the gun measure. The duplicity, he said, also doesn't help.
"It's crazy," Shulman said, "and yes, I think it is intentional."