Roll Call looks at GOP Senators who have formed an opposition nucleus:

This year’s Senate GOP freshman class is a lonely caucus of one, but the seven GOP Senators elected in 2004 quickly are becoming a force to be reckoned with as Republicans adjust to their new minority status in the chamber.

In the two major legislative debates the Senate has held this year, Democrats found that there would be no honeymoon for their new majority, as several up-and-coming Republicans have introduced amendments that have at times bedeviled the opposition.

“These guys are trying to throw all these things out there and hoping something will stick,” noted one knowledgeable Senate Democratic aide. “We just have to be really careful and watch out for it.”

In the first four weeks of the 110th, the “Magnificent Seven,” as the group is known, has produced several notable standouts, including GOP Sens. Jim DeMint (S.C.), David Vitter (La.), Richard Burr (N.C.) and John Thune (S.D.). The other members of the class of 2004, which meets once a month for breakfast or dinner to talk generally about upcoming policy issues, are Sens. Mel Martinez (Fla.), Tom Coburn (Okla.), and Johnny Isakson (Ga.), and they recently invited the lone 2006 Republican freshman, Sen. Bob Corker (Tenn.), to join them, said Burr.

Coburn has been active in the past two years fighting against earmarks in spending bills. Martinez and Isakson have proceeded with a lower-key approach to the chamber, and Corker is still getting his sea legs.

Still, Thune said they meet as a group with Senate GOP leaders to pressure them “in a friendly way” to incorporate their concerns and issues in the Republican floor strategy.

“We’re probably as organized a group as you get in the Senate,” said Thune, who noted that all seven are “pretty ideologically similar.”

Well, I wouldn’t put Martinez in the same class. But the rest are encouraging.