Joe Biden and the Democratic Party believe they are on their way to a decisive victory on Nov. 3, and they may be right. He could find himself in the presidency with his party in control of Congress. But they should beware the pitfall of hubris. The fatal temptation in a moment of triumph is to overreach, and Democrats are already at risk of trying to grab too much.

One of the worst parts of the debate for Kamala Harris came when Mike Pence demanded to know whether, if elected, Joe Biden would "pack the court if Judge Amy Coney Barrett is confirmed." Harris did an extended dance of evasion, allowing her rival to respond, in one of his rare moments of truthfulness, "You, once again, gave a nonanswer."

When asked about the issue the following day, Biden resorted to overt stonewalling. "You will know my opinion on court-packing when the election is over," he said.

Some Democrats, however, are willing to answer the question of whether they would respond to Barrett's confirmation by adding more justices, letting Biden the deprive conservatives of their long-sought, hard-won majority. Their answer is yes.

Sen. Edward Markey of Massachusetts said that if Republicans confirm Barrett, "We must expand the court." Senate Minority Leader Chuck Schumer has warned that if Democrats capture the Senate as well as the White House, "Nothing is off the table." Several progressive groups are pushing this option.

During the primaries, Biden dismissed it. But with many in his party furious over the prospect of an archconservative replacing Ruth Bader Ginsburg, he may think he shouldn't dash their dream just yet. Or maybe he's changed his mind. But it's a mistake to encourage the fantasy, and it would be an even bigger one to pursue it.

The advocates say the court's size has changed several times, so there is nothing unusual about expanding it. But expanding it to shift the court's ideological balance would be highly unusual. The last time it was attempted was in 1937, when President Franklin Roosevelt sought to add justices who would approve his New Deal programs.

A debacle ensued. "Roosevelt woefully underestimated the strength of popular devotion to the court's traditional role," wrote historian David M. Kennedy in his book, "Freedom From Fear." "From the moment of its unveiling, his court plan stirred a nest of furies whose destructive power swiftly swelled to awesome proportions."

It not only failed; it stymied his efforts to enact additional New Deal measures. It also kneecapped his party. Democrats lost a staggering 72 House seats in the 1938 elections, along with seven Senate seats.

To try to mold the court by any means except making appointments when vacancies occur would not be playing with fire; it would be self-immolation. Even many Americans who object to Barrett's nomination would recoil from this remedy. It would make Democrats look as unscrupulous as Mitch McConnell.

The effort would likely fail because moderate Democratic senators would refuse to go along. In that case, Biden would suffer the political fallout for trying while leaving the court untouched — and, if anything, more hostile.

The motive for expanding the court is wholly understandable. The Barrett nomination is an excruciating disappointment. Liberals fear that a commanding conservative majority on the court will reverse progress on abortion rights, health care, the environment, voting rights and more. They will never forgive McConnell for blocking Barack Obama's nomination of Merrick Garland.

Shaping the court, as conservatives understood, requires patience and resolve, but above all, it requires long-term success at the polls. For Democrats to attempt a short cut would endanger their prospects in 2022 and possibly beyond. They should keep their eyes on the prize of winning elections year in and year out.

If they fail at that, then they'll doom their hopes of ever moving the court in a liberal direction. If they succeed, then even a conservative court may feel pressure to moderate. And if Democrats gain and keep power, then they can circumvent adverse judicial rulings on many issues.

Overcoming the damage Donald Trump and his allies in Congress have done to the court will take years if not decades. To do that, Democrats need to win not one election but several. If they're not ready for a long game, then they have no business playing.

Steve Chapman blogs at http://www.chicagotribune.com/news/opinion/chapman. Follow him on Twitter @SteveChapman13 or at https://www.facebook.com/stevechapman13. To find out more about Steve Chapman and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.