The Senate early Thursday morning adopted a Republican budget blueprint that would pave the way for a $70 billion increase for immigration enforcement and the eventual reopening of the Department of Homeland Security.

Republicans pushed through the plan on a nearly party-line vote of 50 to 48. It came after an overnight marathon of rapid-fire votes, known as a vote-a-rama, in which the G.O.P. beat back a series of Democratic proposals aimed at addressing the high cost of health care, housing, food and energy. The debate put the two parties’ dueling messages on vivid display six months before the midterm elections.

Republicans, who are using the budget plan to lay the groundwork to eventually push through a filibuster-proof bill providing a multiyear funding stream for President Trump’s immigration crackdown, used the all-night session to highlight their hard-line stance on border security, seeking to portray Democrats as unwilling to safeguard the country.

Democrats tried and failed to add a series of changes aimed at addressing cost-of-living issues, seizing the opportunity to hammer Republicans as out of touch with and unwilling to act on the concerns of everyday Americans.

Here’s what to know about the budget plan and the nocturnal ritual senators engaged in before adopting it.

Republicans are seeking a way around a filibuster on D.H.S. funding.

The budget blueprint is a crucial piece of Republicans’ plan to fund the Department of Homeland Security and end a shutdown that has lasted for more than two months. After Democrats refused to fund immigration enforcement without new restrictions on agents’ tactics and conduct, the G.O.P. struck a deal with them to pass a spending bill that would fund everything but ICE and the Border Patrol. Republicans said they would fund those agencies through a special budget bill that Democrats could not block.

“We can fix this with Republican votes, and we will,” said Senator Lindsey Graham, Republican of South Carolina and the Budget Committee chairman. “Every Democrat has opposed money for the Border Patrol and ICE at a time of great peril.”

In resorting to a new budget blueprint, Republicans laid the groundwork to deny Democrats a chance to stop the immigration enforcement funding. But they also submitted themselves to a vote-a-rama, in which any senator can propose unlimited changes to such a measure before it is adopted.

The budget measure now goes to the House, which must adopt it before lawmakers in both chambers can draft the legislation funding immigration enforcement. That bill will provide yet another opportunity for a vote-a-rama even closer to the November election.

Democrats used the moment to hammer Republicans on affordability.

Democrats took to the floor to criticize Republicans for supercharging funding for federal immigration enforcement rather than moving legislation that would address Americans’ concerns over affordability.

“This is what Republicans are fighting for,” said Senator Chuck Schumer, Democrat of New York and the Democratic leader. “To maintain two unchecked rogue agencies that are dreaded in all corners of this country instead of reducing your health care costs, your housing costs, your grocery costs, your gas costs.”

Democrats offered a host of amendments along those lines, all of which were defeated by Republicans — and that was the point. The proposals were meant to put the G.O.P. in a tough political spot, showcasing their opposition to helping Americans afford high living costs. Fewer than a handful of G.O.P. senators crossed party lines to support them.

Republicans blocked Democrats’ proposals to address high living costs.

The G.O.P. thwarted an effort by Mr. Schumer to require that the budget measure lower out-of-pocket health care costs for Americans. Two Republicans who are up for re-election this year, Senators Susan Collins of Maine and Dan Sullivan of Alaska, voted with Democrats, but the proposal was still defeated.

Republicans also squelched a move by Senator Ben Ray Lujan, Democrat of New Mexico, to create a fund that would lower grocery costs and reverse cuts to food aid programs that Republicans enacted last year. Ms. Collins and Mr. Sullivan again joined Democrats.

Also defeated by the G.O.P.: a proposal by Senator John Hickenlooper, Democrat of Colorado, to address rising consumer prices brought on by Mr. Trump’s tariffs and the war in Iran; one by Senator Edward J. Markey, Democrat of Massachusetts, to require the budget measure to address rising electricity prices, and another by Mr. Markey to create a fund to bring down housing costs.

Senator Jon Ossoff, a Democrat who is up for re-election in Georgia, also sought to add language requiring the budget plan to address health insurance companies denying or delaying access to care, but that, too was blocked by Republicans.

Republicans sought to amplify their hard-line messages on immigration, voter I.D. and transgender care.

While Republicans had fewer proposals for changes to their own budget plan, they also sought to offer measures that would underscore their aggressive stance on immigration enforcement and dare Democrats to vote against them.

Mr. Graham offered an amendment to allocate funds toward a deficit-neutral reserve fund relating to the apprehension and deportation of adult immigrants convicted of rape, murder, or sexual abuse of a minor after illegally entering the United States. It passed unanimously.

Senator Josh Hawley, Republican of Missouri, sought to bar Medicaid payments to Planned Parenthood, which provides abortion and other services, and criticized the organization for providing transgender care to minors. Senator John Kennedy, Republican of Louisiana, also attempted to tack on the G.O.P. voter identification bill, known as the SAVE America Act. Both proposals were blocked when Democrats, joined by a few Republicans, voted to strike them as unrelated to the budget plan.

The Republicans who crossed party lines to oppose their own party’s proposals for new voting requirements were Ms. Collins along with Senators Mitch McConnell of Kentucky, Lisa Murkowski of Alaska and Thom Tillis of North Carolina.

Ms. Collins and Ms. Murkowski also opposed the effort to block payments to Planned Parenthood.

Just two weeks ago, President Trump threatened to wipe out Iran’s civilization if it did not open the Strait of Hormuz. Days later, he said any Iranian “who fires at us, or at peaceful vessels, will be BLOWN TO HELL!”

Yet on Wednesday, after Iran seized two ships near the Strait of Hormuz, the White House was quick to argue the action was not a deal breaker for potential peace negotiations.

“These were not U.S. ships,” Karoline Leavitt, the White House press secretary, said on Fox News. “These were not Israeli ships.” Therefore, she explained, the Iranians had not violated a cease-fire with the United States that Mr. Trump has extended indefinitely.

She cautioned the news media against “blowing this out of proportion.”

The surprisingly tolerant tone from the White House suggests Mr. Trump is not eager to reignite a war that he started alongside Israel on Feb. 28 — a war that has proved unpopular with Americans and has gone on longer than he initially estimated.

The president on Tuesday extended a cease-fire between the United States and Iran that had been set to expire within hours, saying he wanted to give Tehran a chance to come up with a new proposal to end the war.

The American military has displayed its overwhelming might during the war, successfully striking thousands of targets. But it remains unclear whether Mr. Trump will accomplish the political objectives of the war.

The Iranian regime, even after its top leaders were killed, is still intact. Iran has not agreed to Mr. Trump’s demands to turn over its nuclear capabilities to the United States or significantly curtail them. And the Strait of Hormuz, a key passageway for world commerce that was open before the war, remains closed.

Nevertheless, the White House has repeatedly highlighted the military successes on the battlefield as evidence it is winning the war.

“We have completely confused and obliterated their regime,” Ms. Leavitt said on Fox Wednesday. “They are in a very weak position thanks to the actions taken by President Trump and our great United States armed forces, and so we will continue this important mission on our own.”

The oscillation between threats and a more conciliatory tone has long been one of Mr. Trump’s signature negotiating strategies.

Potential peace talks between the two countries are on hold. Vice President JD Vance had been poised to fly to Islamabad for negotiations. But the trip was postponed until Iran can “come up with a unified proposal,” Mr. Trump said.

The United States recently transmitted a written proposal to the Iranians intended to establish base-line points of agreement that could frame more detailed negotiations. The document covers a broad range of issues, but the core sticking points are the same ones that have bedeviled Western negotiators for more than a decade: the scope of Iran’s uranium enrichment program and the fate of its stockpile of enriched uranium.

Mr. Trump has not spoken publicly about the cease-fire, other than on social media. On Wednesday, he also posted about topics including “my Apprentice Juggernaut” — a reference to his former television show; the Virginia elections, which he called “rigged”; and a new book about Supreme Court Justice Samuel A. Alito Jr.