PHILADELPHIA (CBS) - On Monday -- a week and a day after the Orlando terrorist attack -- the US Senate is expected to vote on gun control legislation.

But it appears a Pennsylvania Republican's amendment will not be among them.

How to keep suspected terrorists from getting their hands on a gun: the measures scheduled to be considered leave Senator Pat Toomey's plan by the wayside.

"We've got two alternatives that are both flawed," he says.

The Republican says his is a compromise, singularly able to prevent the government from running afoul of the right to bear arms.

Toomey calls it a 'continuation' of legislation he and West Virginia Democrat Joe Manchin proposed after the Sandy Hook massacre:

"...To try to ensure that there would be background checks on all commercial gun sales, because I think that's just a common-sense step that does not infringe on any law-abiding citizen's Second Amendment rights."

The two have re-introduced the legislation, its language identical to bills that failed after Newtown and the attack in San Bernardino.