Updated: 8:50 p.m.

Senate Republican leadership, key conservatives and an important moderate Democrat have united on legislation to reform the miscellaneous tariff bill in a way they hope nullifies the ban on earmarks that could ensnare it, Sen. Rob Portman (R-Ohio) told reporters today.

Portman, along with Minority Leader Mitch McConnell (R-Ky.), Minority Whip Jon Kyl (R-Ariz.) and Sens. Jim DeMint (R-S.C.) and Claire McCaskill (D-Mo.), is introducing a bill that would instruct the International Trade Commission to “pre-screen” duty suspension proposals that make up the MTB. Portman indicated that Sens. Roy Blunt (R-Mo.) and John Thune (R-S.D.) worked with him on the bill, but they are not yet co-sponsors.

Portman, a former U.S. trade representative, said the reforms in the bill mean the resulting tariff legislation would not violate House and Senate bans on earmarks and “cleans up a lobbyist-driven process.”

But the approach undercuts House Ways and Means Chairman Dave Camp (R-Mich.), who has argued strenuously that no such reforms are necessary to bypass the earmark ban.

“The current MTB process already has strong support among conservatives, 65 House GOP freshmen and broad bipartisan support in the House and Senate. Chairman Camp is committed to ensuring that our nation’s job creators are not hit with tax increases at the end of the year,” Camp spokeswoman Sarah Swinehart said.

The Portman bill, which tweaks an earlier bill introduced by DeMint and McCaskill, might offer the most plausible route toward passage of an MTB after conservatives raised concerns that Camp’s proposed legislation would violate the ban.

That’s particularly so because it has the vigorous support of DeMint, a conservative icon that could quiet any concerns on the right.

“I strongly support this bipartisan proposal and am thankful to Senators Portman and McCaskill for their work. It’s a critical step forward for earmark reform that will break down unnecessary barriers to small businesses seeking tariff relief.,” DeMint said in a statement.

However, the Senate bill would need Camp’s approval, especially since revenue bills must originate in the House.

The Portman bill would grant significant new authority to the ITC and allow anyone — not just lawmakers — to propose a duty suspension that would then be screened by the commission.

Camp may not be willing to part with that authority.