About once a month, a dozen or so of the country’s most influential Republicans meet in a bare-walled conference room in Washington to discuss how to make further gains in the Congressional elections next year and defeat President Obama.

They share polling and opposition research, preview their plans for advertising and contacting voters in swing states, and look for ways to coordinate spending hundreds of millions of dollars over the next 12 months, drawing on years of experience laboring for the party.

But almost none of them hold office or a job with the Republican Party itself. Instead, they represent conservative groups that channeled tens of millions of dollars into last year’s Congressional campaign. And as 2012 approaches, the groups — among them the Karl Rove-founded American Crossroads, the Republican Governors Association, the American Action Network and Americans for Prosperity, which is backed by the billionaire Koch brothers — have gathered into a loosely organized political machine poised to rival, and in many ways supplant, the official Republican Party apparatus.

At a time when the Republican National Committee remains weighed down by debt, outside conservative groups, freed from contribution limits by the Supreme Court’s Citizens United decision last year, are playing an ever larger role and operating in an increasingly coordinated fashion. In the coming months, the conservative groups will consult among themselves as they open pre-election advertising barrages against Mr. Obama and Congressional Democrats.