The stalemate over a short-term spending bill that has shut down the federal government and furloughed 800,000 employees and contractors offers the latest example of an evolving Republican Party, an evolution that is shifting the party’s traditional power base.

In are conservative activists, who insist that any continuing resolution or debt-ceiling increase be paired with drastic spending cuts and a roll-back of the Affordable Care Act. Out are business and financial interests, which have traditionally held great sway over Republican policymakers.

The conservative activists, led by groups such as Heritage Action and the Club for Growth and elected officials such as Sen. Ted Cruz (R-Texas), are advocating legislative strategies that are doomed to failure in the Democratic Senate but hugely popular with their followers. Business interests are advocating passing the continuing resolution and raising the debt ceiling to avoid economic catastrophe.

It’s clear who’s winning. Cruz has become a darling of those conservative activists, and House Republicans have passed several measures that attach de-funding language to the continuing resolution. On Tuesday afternoon, the House GOP adopted Cruz’s latest tactic, aimed at passing several smaller federal spending measures that would fund the Department of Veterans Affairs, the National Park Service and the District of Columbia. Heritage, under the leadership of conservative godfather and former South Carolina senator Jim DeMint, has raised record amounts of money and goaded activists into pressuring Republican members of Congress.

The U.S. Chamber of Commerce and business interests from across the country, on the other hand, have tried to influence the debate. In a letter sent last week, the Chamber virtually begged Congress to pass a continuing resolution and raise the debt ceiling. What would once have been a powerful message putting Congress on notice failed to move the debate in any meaningful way.

Conservative activists have driven a wedge between business interests and the Republican party on other issues, as well, including immigration and the Farm Bill.

Most Republican leaders read the 2012 elections as a mandate to pass immigration reform, in order to begin what could be a decades-long process to restore the GOP’s relationship with Hispanic voters. Businesses backed a comprehensive reform proposal, as well, and funded paid media campaigns to advocate for its passage.

But after the Senate passed a bipartisan reform measure, conservative activists flexed their muscles again. What once looked like a legislative freight train ground to a halt, as House leaders refused to even consider the Senate-passed bill.

Farm interests have long worked with low-income advocates on a massive package of agriculture subsidies and food stamps. But under pressure from conservative activists — both Heritage and the Club for Growth opposed the joint bill — the House split the two elements in half, before cutting billions from the Supplemental Nutritional Assistance Program. Again, business interests played second fiddle to conservative activists in Congress.

The shift in the Republican power base comes after decades of redistricting processes that put most House seats squarely under one party’s control.

In 1995, the last time the federal government shut down, less than a third of all Republican members of Congress held seats with Partisan Voting Indices of Republican + 10, according to an analysis by David Wasserman of the Cook Political Report. Today, more than half of all Republicans in the House — 122 of 232 — come from districts that fall into that heavily Republican column.

That means members of Congress are more vulnerable in their primaries, where they might face challengers who declare them insufficiently conservative, than they are in general elections. Republican primary voters, who are by definition more conservative than the electorate as a whole, hold disproportionate sway over those incumbents.

Meanwhile, the lucrative contributions from business interests, which for decades have been major sources of campaign cash for Republicans, become less important in a general election, as general elections themselves become less important than primaries. Most of the Republican incumbents who have lost primaries in recent years — including Sen. Lisa Murkowski (R-Alaska), ex-senators Bob Bennett (R-Utah) and Richard Lugar (R-Ind.) and ex-representative Joe Schwartz (R-Mich.), to name a few — have vastly outspent their ultimately successful challengers.

Until the 2010 tea party wave and the rash of primary challenges against incumbent members, the influence of conservative activists built slowly and quietly. Today, as the House prepares yet another iteration of the continuing resolution that the Senate will almost surely reject, the shift of power from business interests to conservative activists is complete.

The shutdown may as well be their coming-out party.