By Lisa Mascaro, Tribune Washington Bureau (TNS)

WASHINGTON — The Senate stayed in session all night to pass a $3.7 trillion Republican budget early Friday, grinding through tough — but symbolic — votes that provided the new Congress with a needed achievement.

Passage on a strict party line vote, 52-46, represented progress for Republicans who have struggled to present a unified front in their first months controlling both the House and Senate.

Even though the budgets are simply road maps for future spending, they hold ideological significance as statements of party principles, especially heading into the 2016 campaign season. Speaker John A. Boehner ushered the House’s $3.8-trillion plan to passage earlier in the week.

Getting to this point was not easy. With Democrats flatly opposed to the Republican budget plan that deeply slashes federal safety net programs, the debate exposed divisions between the Republican Party’s traditional defense hawks and those who prefer to hold the line against extra spending.

The difference spilled over Thursday as Sen. Marco Rubio (R-Fla.) and Sen. Rand Paul (R-Ky.) — both senators who are expected to run for president in 2016 — amplified the issue with competing plans to bolster defense spending.

The Pentagon had already received a sizable bump up after both the House and Senate plans averted spending limits established just a few years ago and added Pentagon funds by using a separate war contingency account unaffected by the limits.

But Paul and Rubio wanted to increase the military money even more. Their proposals, however, had one main difference: Rubio’s plan would have allowed the extra spending to raise the deficit, while Paul’s amendment required that deep cuts be made in education, climate change research and other accounts to offset the costs.

Both of their votes failed, but the outcome clearly established the dominance of the defense hawks. Paul’s amendment won just four backers, including himself and Majority Leader Mitch McConnell. Rubio’s fared better, failing on a vote of 32-68.

In the end, Rubio relented and voted in favor of the final budget, while Paul voted against it, as did Sen. Ted Cruz (R-Texas), also a 2016 presidential aspirant.

“It is irresponsible and dangerous to continue to put America further into debt,” Paul said. “We need national defense, but we should pay for it. … We should be honest with the American people, and pay for it.”

The all-night session, dubbed “vote-a-rama,” always puts senators in a bind on a number of votes, and Thursday’s session was no different.

In between a buffet dinner off the Senate floor catered by McConnell’s office, the senators were forced to choose whether to support paid sick days for workers (approved, 61-39) or impose a temporary war tax to pay for the fight against Islamic State (rejected, 46-54).

The Obama administration’s negotiations with Iran were a topic of debate, with senators supporting an amendment, 59-41, to block money for implementing any agreement until it is approved by the Senate. They also agreed 100-0 to impose new sanctions if Iran violates any deal.

Earlier in the week, President Barack Obama’s own budget was put to a vote in a political move designed to embarrass Democrats. It failed overwhelmingly, 98-1.

Now the two chambers face the daunting task of reconciling their differences if Republicans hope to achieve a top goal — holding a vote to repeal Obama’s health care law under special budget rules that would prevent a filibuster in the Senate.

Mostly, the budgets of the House and Senate align along Republican priorities of lowering taxes, slashing federal spending on social programs and repealing Obama’s health care law. Both Republican budgets poured about $38 billion more into the military than would have been expected had Congress stuck to the earlier limits.

Democrats are led on the Budget Committee by Sen. Bernard Sanders (I-Vt.), who called it “particularly offensive that Republicans, who are demanding massive cuts in Medicaid, education, nutrition and health care in order to move to a balanced budget, have no problem adding $38 billion to Pentagon spending.”

But key differences between the Republican plans remain — including the House’s decision to include the GOP plan for turning Medicare into a new program that would give seniors vouchers that could be used to purchase private health insurance.

Senate Republicans have panned that Medicare overhaul and did not include it in their budget.

Both budgets also claim to balance within the decade, but include the tax revenues from Obama’s healthcare law, even as Republicans are trying to repeal it.

Resolving those issues will be thorny. The House and Senate have not reconciled their budgets since Democrats controlled Congress in 2010, when they too wanted to use special budget procedures to pass Obama’s health care law.

Obama has vowed to veto any legislation that undoes the Affordable Care Act, but that has not stopped Republicans from trying. Now they hope to use the same budget shortcut to try to repeal it.

With lawmakers headed out of town for a two-week spring recess, those votes are expected later this summer.

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Photo: Crazy George via Flickr