As the U.S. Senate gets back to work today, there's a lot on the agenda: A budget plan, immigration reform and the question of creating a universal background check. Slate's John Dickerson explains why he thinks the Senate might actually break through the logjam that has held up legislation in recent years; meanwhile, Talking Points Memo notes that Senate Majority Leader Harry Reid is growing increasing impatient with the GOP's filibustering strategy.

On the subject of the universal background checks: Supporters of expanding the checks to nearly all unlicensed gun sales (which is a contentious step I explored here) are holding out hope that they can bring over Republican Sen. Pat Toomey of Pennsylvania, according to the Washington Post.

Arizona Sen. Jeff Flake has said that expanding those background checks would require too much paperwork; instead, he wants to see more mentally ill people added to the list of prohibited possessors.

During a Sunday appearance on Face the Nation, Arizona Sen. John McCain sidestepped a question over whether he still supported expanding background checks to gun shows, saying that it would depend on how the checks are done.

McCain expressed exasperation with Republican colleagues who are threatening to filibuster the legislation.

"I don't understand it," McCain said. "The purpose of the United States Senate is to debate and to vote and to let the people know where we stand. … What are we afraid of?"