A last-minute effort in the United States Senate to stave off default looks certain to divide Republicans in the House of Representatives, where members thwarted their leader’s attempt at compromise earlier on Tuesday.

House speaker John Boehner was forced to shelve a proposal to reopen the federal government and lift the nation’s $16.7 trillion debt limit in the face of resistance from his most conservative members. They had conditioned support for a new budget on delaying the implementation of President Barack Obama’s health reforms by one year. Democrats rejected this, triggering a government shutdown two weeks ago.

Boehner had proposed to fund the government through January and extend the debt limit into February, giving the parties several more months to work out a compromise. Dozens of conservative members said “no”.

They were strengthened in their resolve by the influential conservative Heritage Action for America group’s opposition to any budget deal that does not stop Obama’s health-care law.

Fractured

Yet the deal reportedly discussed by the Democratic leader in the Senate, Harry Reid, and his Republican counterpart, Mitch McConnell, would offer a similar timetable. Assuming all Democrats in the lower chamber support it, the law would need seventeen Republican votes to pass.

Center-right Republicans may be willing to back such an effort to prevent default and end the shutdown for which they are blamed by most Americans. But by doing so, they would signal that their party is becoming even more fractured.

Earlier this year, House Republicans were also divided over a budget measure that raised taxes for the rich to avert tax hikes on all incomes. Virtually all conservatives from the Southern United States rejected this compromise, because it raised taxes at all. Most Republicans from other regions supported it.

Alliance

The Republican Party has long been an alliance of fiscal and social conservatives from more inland districts and liberals from the coastal regions who not always oppose Democratic social policies and are less reactionary altogether. The former have largely taken over the party.

Members who were endorsed by Tea Party organizations — the populist conservative movement that emerged in 2009 in opposition to the president’s health-care and spending plans — now make up a third of the Republican caucus in the House of Representatives. Nearly half its members are from Southern states. In the Senate, twenty out of 46 members are from the region.

The centrist wing has potential presidential candidates who are more likely to win a national election. Among them is former Florida governor Jeb Bush, who warned in March that Republicans were becoming “too reactionary” and “cannot sustain a message of being against things. You have to be for things.”

Another is New Jersey’s governor Chris Christie, who is expected to be reelected next month. He blames both parties for the shutdown. “If I was in the Senate right now, I’d kill myself,” he told reporters last week.

Expediency

The divide is one of political expediency as well. Unlike Southern congressmen and senators, whose districts and states are so conservative that their only threat to reelection is a primary challenge from the right, Republicans in the rest of the country have to moderate their positions and compromise in order to win elections.

That means the likes of Bush and Christie are far more acceptable to the electorate at large than a Tea Party candidate would be.

And without a Republican in the White House, any bill that repeals Obamacare could be vetoed by a president of the other party.