WASHINGTON — Republicans lined up in opposition to President Biden’s ambitious economic package on Wednesday, even before he was set to detail it in a joint address to Congress, signaling a bitter partisan fight to come over his efforts to increase government assistance to workers, students and families.

Senator Tim Scott of South Carolina was tapped to deliver his party’s rebuttal to Mr. Biden’s speech, spotlighting the sole Black Republican senator who often leans heavily on his extraordinary biography to argue against costly and far-reaching government assistance measures like the ones the president is proposing.

On Wednesday afternoon, some Republicans took to the Senate floor to offer their own rebuttals in advance of Mr. Biden’s evening speech. They painted the president’s two-pronged infrastructure plan — one to bolster the nation’s roads and bridges and another to expand access to education and child care, carrying a total price of just over $4 trillion — as unnecessary, expensive and intrusive government overreach. Their reactions underscored the long odds facing Mr. Biden’s stated goal of pursuing a compromise with Republicans on the package.

“Behind President Biden’s familiar face, it’s like the most radical Washington Democrats have been handed the keys, and they are trying to speed as far left as they can possibly go before American voters ask for the car back,” said Senator Mitch McConnell of Kentucky, the Republican leader. “But it’s not too late. This White House can shake off its daydreams of a sweeping socialist legacy that will never happen in the United States.”

Mr. Scott said he would present an “optimistic” rebuttal to Mr. Biden’s address, outlining an alternative way forward intended to “unite the nation” and underscore conservative values. And the senator plans to attribute the glut of vaccines that has eased the coronavirus pandemic to the Trump administration, according to excerpted remarks released ahead of his speech.

But as Republicans seek to regain majorities in both the House and the Senate in 2022, they are not expected to offer a comprehensive alternative to the president’s latest proposals. Instead, much of their strategy is likely to echo Mr. McConnell’s comments painting Mr. Biden as beholden to his party’s left flank.

That approach was on display on Wednesday as the president was poised to unveil his wide-ranging $1.8 trillion “American Families Plan” that is intended to expand access to education and child care. Republicans argued that such an ambitious expansion of the social safety net was unnecessary, and they warned that it would harm the economy because it would be paid for by reversing a sweeping collection of tax cuts they pushed through in 2017 under President Donald J. Trump.

“What this would do is incentivize women to rely on the federal government to organize their lives,” Senator Marsha Blackburn of Tennessee said Wednesday on Fox Business, calling Mr. Biden’s proposal an “anti-family plan” that would lead to higher taxes. “It takes away from them the ability to organize their family life as they would like to organize it.”

While last week Republicans introduced their own, drastically slimmed down answer to Mr. Biden’s sprawling physical infrastructure package — offering a $568 billion counterproposal that Democrats dismissed as inadequate — they have not offered an education and child care bill.

But some individual senators have introduced significantly narrower pieces of legislation intended to aid families. Senators Joni Ernst of Iowa and Mike Lee of Utah in 2019 introduced a paid parental leave plan. And Senators Mitt Romney of Utah and Josh Hawley of Missouri have both argued in favor of expanding the child tax credit to provide all but the wealthiest families with regular monthly checks.

However, those efforts have faced resistance from other Republicans, some of whom have chafed at any measures that might resemble “welfare assistance.” They also have yet to win the imprimatur of the party’s leaders.

On Wednesday, Mr. Romney expressed skepticism about the total cost of Mr. Biden’s package of economic proposals, calling it “a massive amount of spending.”

“Maybe if he were younger,” Mr. Romney told reporters, “I’d say his dad needs to take away the credit card.”

Senator Thom Tillis, Republican of North Carolina, took to the Senate floor to accuse Mr. Biden of pushing unnecessary “partisan policies.”

“When you think about infrastructure, you think about roads, you think about bridges, you think about broadband,” Mr. Tillis said. “You don’t think about human infrastructure, but that’s what’s being pitched today. And it’s being pitched on a partisan basis, without even attempting to get a single Republican vote.”

A prompt counterproposal is unlikely to come from the House, either. Top Republicans in that chamber selected members this week to begin drafting a broad array of legislation on jobs and the economy, “the future of American freedoms” and other issues that are expected to shape their agenda leading up to the midterm elections.