Republican backers of a once-in-a-generation gun violence bill now lead the charge against one part of the Biden administration’s implementation of the law, a falling out that illustrates the delicacy of trust required to pass legislation on hot-button issues.

A Congressional Review Act joint resolution of disapproval introduced Wednesday in the Senate by John Cornyn, R-Texas, could force the chamber to vote on overturning a rule from the Bureau of Alcohol, Tobacco, Firearms and Explosives that would expand the number of gun sellers who would be required to run background checks.

U.S. Sen. John Cornyn doesn’t hide that he wants Mitch McConnell’s job as Senate Republican leader.

The senior Texas senator has long expressed interest in the position and spent years as McConnell’s top deputy. After a recent series of health scares raised concerns about McConnell’s future, questions abound about Cornyn’s next step.

Cornyn has said that he will continue to support McConnell as party leader, calling him “extraordinarily effective” during the 2021 Texas Tribune Festival.

As House GOP leader Kevin McCarthy forges ahead in his quest to secure 218 votes to be the next speaker of the House, he is vowing to take a hard line in the future against any GOP senator who votes to pass the $1.7 trillion spending bill this week.

McCarthy wrote on Twitter, “when I’m Speaker,” bills from any senator who votes for the spending package will be “dead on arrival” in the House of Representatives. He was responding to a letter from Rep. Chip Roy, a conservative who has not said yet if he will back McCarthy for Speaker.

Senate Republicans on Tuesday shrugged off a vow from House Minority Leader Kevin McCarthy (R-Calif.) to block the legislative priorities of any GOP senator who votes for the $1.7 trillion omnibus spending bill.

Why it matters: Senate Republicans are saying what their House counterparts can't — that McCarthy's tough talk is intended to win over the conservatives whose votes he needs to become speaker and that he won't follow through.

House Minority Leader Kevin McCarthy (R-CA) is threatening to tank the legislation of Senate Republicans who back the omnibus spending bill being considered this week, setting up a showdown with his counterpart, Senate Minority Leader Mitch McConnell (R-KY).

Sen. John Cornyn (R-Texas), the top Republican negotiator for the Senate’s newly unveiled gun control bill, has said he will not take part in a new round of gun control talks concerning proposals aimed at limiting access to certain rifles or expanding background checks.

A key sticking point in the negotiations over a bipartisan gun violence package being drafted in the Senate has become how states can use grant money in that package.

The framework released Sunday called for grant money to help states implement “red flag” laws, which allow law enforcement and family members to petition courts to temporarily remove firearms from people who show signs of becoming dangerous to themselves or others.

Top negotiators on a bipartisan gun safety framework deal huddled behind closed doors for several hours Wednesday evening to try to solve remaining differences, but the group's effort to expedite passage of an agreement is stalled, at least for the moment.