Now that it’s Trump v. Biden, it’s a bit easier to game out the direction of the 2020 presidential election. The withdrawal of Bernie Sanders from the Democratic race leaves former Vice President Joe Biden with nobody to focus on but President Trump, while Trump now knows he can hammer away at “Sleepy Joe” rather than “Crazy Bernie.”

The coronavirus pandemic and the economic collapse it has caused obviously make it a volatile election, with surprises ahead. But it’s also clear that Trump faces a tough challenge, given that no president in 70 years has been re-elected in the midst or the aftermath of a recession—especially one as severe as the coronavirus recession is likely to be.

Democratic pollster Stanley Greenberg recently joined the Yahoo Finance Electionomics podcast and outlined the risks he sees for Trump in his survey results. Here are three:

Biden is strong in swing states. Greenberg’s polling closely follows voters in 16 battleground states, including Pennsylvania, Ohio, Michigan and Wisconsin. Trump won the battleground states by 1 percentage point against Hillary Clinton in 2016—giving him enough electoral votes to clinch the election. But Biden is ahead of Trump so far in 2020. “Biden’s winning by 4 to 5 points,” Greenberg says. “If Hillary won the popular vote by 2 nationally, that would translate to 7 for Biden.” And that’s enough for him to win.

Biden’s margin at the moment isn’t as large as the 9-point advantage Democrats had in the 2018 midterms. But that could reflect Sanders’ role in the race. Since Sanders stayed in until April 8, he could have detracted from Biden’s performance against Trump up to that point. With Sanders out, some voters have a simpler choice, which could benefit Biden. That’s not a given, but Sanders is more chummy with Biden now than he was with Clinton in 2016, which could swing more of the Sanders vote toward Biden.

The Republican party is shrinking. “There’s been a revolt against Trump that people just haven’t paid attention to,” Greenberg tells Yahoo Finance. “The Republican party has been shedding voters.” That’s not apparent in Gallup’s survey of party affiliation, which shows the GOP with a relatively stable 30% share of the electorate nationwide. But Greenberg and other pollsters say they’ve seen surprising shifts in battleground states during the primary elections.

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In Michigan, for instance, there was a notable increase in turnout in the Democratic primaries—in some predominantly Republican areas. That suggests some moderate Republicans aren’t just turning on Trump—they’re also switching parties. “I thought moderate Republicans who have pulled away from Trump, maybe by November they’d vote for Biden,” Greenberg says. “But they’re voting in the Democratic primaries.”

FILE - In this combination of file photos, former Vice President Joe Biden speaks in Wilmington, Del., on March 12, 2020, left, and President Donald Trump speaks at the White House in Washington on April 5, 2020. Barring unforeseen disaster, Biden will represent the Democratic Party against Trump this fall, the former vice president's place on the general election ballot cemented Wednesday, April 8, by Bernie Sanders' decision to end his campaign. (AP Photo) More

Voters judge a president on the last six months. The state of the economy will obviously be a major factor in the November elections, given a massive surge in unemployment and lost earnings for millions as they go to vote. It’s possible the economy will be recovering by then, allowing Trump to claim credit for defeating the virus and getting the country back on track. But there’s almost no chance employment or economic output will be back to pre-virus levels by then, and many voters won’t care how good the economy was before the virus arrived.

“People will say to themselves, ‘am I making gains now, and in the last six months?’” Greenberg says. “They don’t have a longer time frame on it.” That means Trump’s many boasts about “jobs, jobs jobs” and record stock market highs won’t count for much.

Biden, 77, has vulnerabilities. He’s not a gifted speaker or TV personality and he doesn’t excite many voters. His frequent flubs invite speculation that he’s slowing, mentally—a meme already rampant in conservative media.