Joe Biden’s unexpectedly rapid consolidation of the Democratic presidential nomination has upended calculations in both parties about the U.S. Senate landscape, with Democrats hopeful that Biden can actively help with close races and Republicans increasingly nervous about losing their 53-47 majority.

Biden’s ascent has dented GOP plans to paint Democratic candidates as left-wing extremists, something they were eager to do had Sen. Bernie Sanders (I-Vt.) emerged as the nominee. Instead, the Democrats now have a more moderate standard-bearer who is intimately familiar with the Senate, in close touch with top candidates and keenly aware of how Senate control could affect his potential presidency.

The former vice president’s emergence is part of a larger shift in prospects that has become clear in states such as Arizona, Colorado, North Carolina and even Montana and Georgia, as a surge in Democratic fundraising, along with President Trump’s struggles to manage the coronavirus pandemic, have led independent analysts to upgrade Democrats’ chances.

Even in Alabama, one of the most conservative states, underdog Sen. Doug Jones (D) stands an outside chance of an upset, a fact that Jones attributes in part to Biden besting Sanders.

“Was it in fact a relief? Sure, it was a relief — for me and I think a lot of the moderate Democrats that won in 2018,” said Jones, who has known Biden for decades and spoke to him this month. “It’s always tougher to run when you’ve got somebody on the ticket that is identified as far more liberal than you are.”

Beyond the Senate’s critical role in passing legislation and confirming judges and Supreme Court justices, Biden served 36 years in the chamber, which formed him politically and shaped many of his friendships. He has repeatedly engaged in behind-the-scenes efforts to boost the party’s chances of winning the majority.

In the final sprint to the Iowa caucuses in mid-January, when Biden’s own nomination was in serious doubt, he hopped on the phone with Montana Gov. Steve Bullock to urge him to consider running for the Senate. He had a similar talk with former Colorado governor John Hickenlooper.

Bullock and Hickenlooper, both of whom ran against Biden for the presidential nomination, are now two of the Democrats’ marquee Senate prospects. Biden consulted Senate Minority Leader Charles E. Schumer (D-N.Y.) before both conversations, according to people with knowledge of the discussions

Just this past week, the former vice president was on the phone with his friend Sen. Christopher A. Coons (D-Del.), taking inventory of which candidates were “looking strong” and which were in “need of some additional support,” Coons recalled.

Biden is even eager to discuss the Senate when talking to those more interested in the House, raising the issue a few days ago with Rep. Cheri Bustos (D-Ill.), the chair of the House Democratic campaign arm. “We talked a little bit about the Senate,” Bustos said. “He’s very optimistic about what’s ahead.”

Nonpartisan analysts and strategists in both parties agree that the Senate landscape has shifted in recent weeks, pushing Democrats to within striking distance of a takeover. The pandemic and the collapse of the economy, once Trump’s biggest strength, are big factors, but so is Biden’s rise.

“Biden’s likely nomination was critical to Democratic chances of taking back the Senate because it keeps the battlefield large,” said Nathan Gonzales, editor and publisher of Inside Elections. “I think if Democrats had nominated Sanders, it would have limited Democratic takeover opportunities.”

Trump, too, is sharply aware of the Senate’s importance. He and Senate Majority Leader Mitch McConnell (R-Ky.) spoke about the outlook in late February, according to a person with knowledge of the discussion. Read more

Also read Coronavirus: Italy’s PM outlines lockdown easing measures