“Her election would mire our government and our country in a constitutional crisis that we cannot afford,” Trump declared Monday in Grand Rapids, Michigan, pointing to the FBI’s renewed examination of Clinton’s email practices as evidence the former secretary of state might face a criminal trial as president.

National polls show a tightening race. But with more than 23 million ballots already cast through early voting, it’s unclear whether Trump has the time or capacity to dramatically improve his standing over the next week in states like Michigan, where few political professionals in either party expect a Republican victory on Nov. 8.

Clinton, defending herself from the new FBI examination, focused Monday on battleground Ohio, a state Trump’s team concedes he must win.

“There is no case here,” Clinton insisted. “Most people have decided a long time ago what they think about all this.”

Later in the day, Clinton campaign manager Robby Mook decried what he called a “blatant double standard” following a CNBC report that FBI Director James Comey opposed releasing details about possible Russian interference in the U.S. election because it was too close to Election Day. Comey issued a letter to congressional leaders on Friday about the FBI’s renewed interest in Clinton’s email.

The AP has not confirmed the CNBC report, and the FBI declined comment Monday.

Meanwhile, the ongoing mystery of Trump’s tax returns arose again. The New York Times reported Monday night that in the 1990s, Trump avoided paying potentially hundreds of millions of dollars in taxes in a way even his own lawyers considered questionable, using a maneuver Congress explicitly banned in 2004. Trump spokeswoman Hope Hicks said Trump’s approach was appropriate.

Amid the attacks and counterattacks, the race for the White House remains a test of a simple question: Will the conventional rules of modern-day campaigns apply to a 2016 election that has been anything but conventional?

For much of the year, Clinton has pounded the airwaves with advertising, assembled an expansive voter data file and constructed a nationwide political organization that dwarfs her opponent’s.

The Democratic presidential nominee and her allies in a dozen battleground states have more than 4,800 people knocking on doors, making phone calls and otherwise working to support her candidacy. Clinton’s numbers, as reported in recent campaign filings, tripled those of Trump and the national and state Republican parties.

The New York businessman over the past year has largely ignored the key components of recent winning campaigns, depending instead on massive rallies and free media coverage to drive his outsider candidacy. This week, he’s devoting his most valuable resource—his time—to states where polls suggest he’s trailing Clinton by significant margins.

Trump had two rallies Monday in Michigan, a state that last went for a Republican presidential nominee in 1988. The day before, he appeared in New Mexico, which has supported the GOP just once over the last three decades. And on Tuesday, he’s scheduled to appear with running mate Mike Pence in Wisconsin, which hasn’t backed a Republican for president since Ronald Reagan’s re-election in 1984.

Trump’s campaign hopes that frustrated working-class voters across the Midwest will tip states like Michigan or Wisconsin his way, especially if he benefits from reduced enthusiasm for Clinton in African-American strongholds like Detroit and Milwaukee. New Mexico is seen as a longer shot, with Trump’s hard-line immigration stance a harder sell in a state with the nation’s highest percentage of Latino voters.

Adding to Trump’s challenge: Millions have already voted by mail and at polling stations across 37 states. They include critical states such as Florida, Nevada and Colorado, where one-third of the expected ballots have already been cast.

Meanwhile, some Republicans are skeptical that the FBI’s renewed interest in Clinton’s email will erase the Democrat’s advantage.

“It would take something like an indictment to turn it into a dead heat,” Republican pollster Whit Ayres said.

As for Trump’s charge that a Clinton election might prompt “a constitutional crisis,” the Justice Department’s office of legal counsel said in 1973 that criminally prosecuting a president would unconstitutionally undermine the executive branch. A 2000 memo reached a similar conclusion. Presidents can face civil lawsuits, however.