More Senate Republicans are starting to break from their party to support new gun control measures.
Sen. Susan Collins of Maine said this weekend she would vote for a compromise on background checks. That compromise was crafted by Sens. Patrick Toomey, R-Pa., and Joe Manchin, D-WV.
The proposal requires background checks for people buying guns at gun shows and online, but exempts private gun sales.
Sen. John McCain, R-Ariz., also said on Sunday he was "very favorably disposed" to support a gun measure, but he did not officially commit to vote for it.
Advocates say the measures would make it harder for criminals and the mentally ill to get weapons.
Opponents argue that the restrictions would violate the U.S. Constitution's right to bear arms and would be ignored by criminals.
Right now only three Republican senators are expected to vote for the compromise bill. Senate Democrats need every vote they can get. A vote is expected this week and it's too close to call.