National polls suggest an edge for Joe Biden in Tuesday's contest against President Donald Trump, but the winner won't necessarily the candidate with the most votes. It's whoever wins the Electoral College, a system set up by the Constitution (see video below). Victory is won in the largest states, as Hillary Clinton's 2016 loss showed. (She had 3 million more votes overall, but Donald Trump led in states that swung the outcome -- the fifth time in U.S. history that a president was elected without a popular vote majority.)

The Electoral College, which has nothing to do with higher education or a campus, is a body of electors that forms every four years to elect the president and vice president. It consists of 538 electors pledged to candidates that won each state (except in Maine and Nebraska, which award electoral votes more proportionally. The total pool of electors represent the number of U.S. senators, 100 (two per state); the number of state representatives, 435; and three more electors for the District of Columbia. At least 270 electoral votes (a majority) are needed to win.

Some experts see six states as the top electoral prizes this time. Three are northern battlegrounds that Donald Trump carried four years ago by less than a percentage point: Wisconsin, Michigan and Pennsylvania. The others are Sun Belt states where Trump's 2016 margins were a little bigger: Arizona, Florida and North Carolina.

In any event, official results are likely to be unclear past Tuesday night because millions of absentee ballots were mailed or dropped off by voters hesitant to risk crowded polling places during the pandemic. Counting those could delay a confirmed outcome for several days -- maybe even a week or two -- because each ballot must be manually removed from an envelope and verified as valid before being fed into a tabulating machine. In a half-dozen states, including Pennsylvania and Wisconsin, processing can't start until Election Day. "States like Pennsylvania may be counting mail-in ballots for weeks," writes Ben Smith, a New York Times columnist, "while President Trump tweets false allegations about fraud." Trump has signaled that he may prematurely declare himself winner and try in court to invalidate some mailed ballots. Facebook, Twitter and YouTube pledge to crack down on misinformation about voting and election results. At the government level, each state has until Dec. 8 this year to resolve any controversy over the appointment of its slate of electors. Those electors meet in their states Dec. 14 and formally cast votes for president and vice president, who'll be inaugurated Jan. 20.

Trump says: "We want to make sure the election is honest, and I'm not sure that it can be." – President to reporters, Sept. 24

Biden says: "The people in the country are going to be heard on Nov. 3. Every vote in this country is going to be heard and they will not be stopped. I'm confident that all of the irresponsible, outrageous attacks on voting, we'll have an election in this country as we always have had."

Columnist says: "It's hard to imagine things proceeding in an orderly way [after polls close] unless Trump wins in a landslide." – Margaret Sullivan, Washington Post media columnist