On his 100th day ruling the House, Speaker John A. Boehner (R-Ohio) watched a quarter of his troops abandon him.

Boehner’s leadership team relied on a large bloc of Democrats on Thursday to muscle through the spending bill that was the product of six weeks of negotiations with the White House and Senate Democrats.

With the fight over funding the federal government for the rest of the fiscal year behind him, Boehner is heading into a much more difficult and consequential showdown on raising the limit on the nation’s credit card with a potentially weaker hand.

The federal debt ceiling, currently just under $14.3 trillion, is projected to be breached by mid-May, and the Treasury Department’s accounting tricks will last only until early July. Boehner has promised to oppose raising the debt limit unless Democrats agree to budget reforms, setting the stage for another protracted and acrimonious negotiation.

Boehner’s leadership team will begin those talks with a problem among many conservatives, as evidenced Thursday afternoon when 59 Republicans — a quarter of the GOP caucus — rejected the 2011 spending bill as too timid.

Some of them opposed the measure because the Congressional Budget Office said on Thursday that the bill probably would cut far less than the advertised $38 billion amount. Boehner, House Majority Leader Eric Cantor (R-Va.) and House Majority Whip Kevin McCarthy (R-Calif.) all strenuously backed the deal, but that wasn’t enough to stem the conservative uprising.

Recognizing the small rebellion at hand, Boehner sidestepped any chance of taking a victory lap. He told reporters Thursday that it was no cause for “celebration” and that his biggest accomplishment so far was changing the nature of the discussions.

“Is it perfect? No,” he said during House debate. “I’d be the first to admit it’s flawed. But welcome to divided government.”

In the end, Boehner’s team relied on what might be called a 75-40 coalition: 75 percent of his Republican rank and file, along with 40 percent of Democrats, supported the pact.

An almost identical coalition provided the decisive votes for a stopgap funding resolution this spring, when 54 Republicans rejected that earlier Boehner-led compromise.

Even Boehner’s closest friends have said the mid-March vote weakened him politically as he entered the most difficult negotiations on the spending bill, leading to an effort to reunify the Republicans last week for the final days of the high-stakes talks.

The speaker’s team said Thursday that he has the broad support of an overwhelming majority of his party, with seven in 10 freshmen voting for the spending bill.

However, Thursday’s vote demonstrated that at least 50 Republicans are prone to reject almost any compromise with President Obama and Senate Majority Leader Harry M. Reid (D-Nev.). Conservatives, particularly freshmen, have voiced deeply ingrained opposition to raising the debt ceiling — an issue that has reached a fevered pitch among tea party activists who are demanding that their lawmakers shrink the government.

In that debate, the stakes will be higher. Treasury Secretary Timothy F. Geithner and others have warned of dire consequences to the global financial markets if the debt limit is not extended and the government begins defaulting on its loans.

In past votes on the debt limit, the minority has generally demagogued the issue and forced the majority to approve it. Then-Sen. Obama did just that in 2006, acknowledging in an ABC interview on Thursday that his vote against raising the debt ceiling was “a new senator, you know, making what is a political vote as opposed to doing what was important for the country.”

Reid and House Minority Whip Steny H. Hoyer (D-Md.) recanted this week their past votes against lifting the debt ceiling while they served the minority.

This could set the stage for Democrats to again provide the decisive margin for the critical measure.

After the March vote, McCar­thy met with a group of moderate Democrats to discuss their willingness to support broader fiscal reforms later this year. And on Wednesday, McCarthy phoned Hoyer to ask how many Democrats would support the 2011 funding bill to ensure enough votes for the deal to pass, said an aide familiar with the conversation.

With debate over the debt limit intensifying, Republicans are discussing attaching some tough statutory language to the bill that would allow the ceiling to be increased only if Congress institutes broad spending cuts in federal agency budgets and in entitlement programs such as Medicare.

Those proposals might unify House Republicans for an initial passage of the debt ceiling, but they might also fail in the Democratic-controlled Senate.

Such an outcome would send Boehner back to the bargaining table with Obama and Reid. This past week’s reaction to the spending bill from GOP conservatives may leave the White House assuming Boehner will not be able to deliver a majority on his own, prompting Obama’s side to not give in to as many of the speaker’s demands.

Staff writers Felicia Sonmez and David A. Fahrenthold contributed to this report.