Is President Biden Ready for the New Senate?

In the Senate, more than a quarter of the seats have changed parties in the past four years — including five of the Republicans who praised Mr. Biden at that 2016 event. Many of the new members are products of the deeply polarized Trump era and have never served in a more functional Senate.

Some of Mr. Biden’s closest aides believe the attack on the Capitol broke the fever within the Republican Party, creating space for its elected officials to work across the aisle. Yet, there are plenty of signs that former President Donald J. Trump’s influence on his party may linger.

While the former president’s approval rating dropped sharply among Republicans after the attack, Trumpism remains embedded in the firmament of the party. Plenty of Republican state officials, local leaders and voters still believe Mr. Trump’s baseless claims of election fraud and view Mr. Biden as illegitimate. They’re threatening primary challenges against Republicans who work with Mr. Biden, complicating the political calculus for members of Congress, including several up for re-election next year, like Senators Rob Portman of Ohio and Lisa Murkowski of Alaska, who might be inclined to cut some legislative deals.

Already, Mr. Biden’s proposed $1.9 trillion pandemic relief plan has received a skeptical response from Republicans, including several centrists who helped craft the economic package that passed late last year. Senator Roy Blunt of Missouri, chairman of the Senate Republican Policy Committee, called the proposal a “non-starter.”

“We just passed a program with over $900 billion in it,” Senator Mitt Romney, Republican of Utah, told reporters shortly after the inauguration. “I’m not looking for a new program in the immediate future.”

And then, there’s the issue of Mr. Biden’s own party. After four years of Mr. Trump, many Democrats are unwilling to compromise on their agenda. A vocal portion of the party is pushing to pass Mr. Biden’s rescue package through a budget resolution that would allow the legislation to clear the Senate with just 51 votes, instead of the usual 60 votes.

Mr. Reid is urging Mr. Biden not to waste much time trying to win over his former Republican colleagues. Like many Democrats, he’d like Mr. Biden to eliminate the legislative filibuster — the 60-vote requirement for major bills — allowing Democrats to pass their agenda with their slim majority.