More Americans than usual are expected to vote by mail this year because of Covid-19 fears about lining up at polling stations. Slightly more than half the respondents in a May poll by New Jersey's Monmouth University said they'd cast absentee ballots. But mail-in ballots are a touchy topic lately, with President Trump voicing "rigged election" concerns repeatedly – even though he customarily votes by mail. The Republican National Committee and two other groups filed a lawsuit challenging California's expansion of the method. The state's Democratic governor, Gavin Newsom, wants counties to mail absentee ballots to all registered voters. Many other states, led by Republican as well as Democrats, plan to send absentee ballot request forms to all voters and then provide ballots for those requesting them.

"There is NO WAY (ZERO!) that Mail-In Ballots will be anything less than substantially fraudulent," Trump tweeted last week. "Mail boxes will be robbed, ballots will be forged & even illegally printed out & fraudulently signed." In the first such step, Twitter put warnings on two presidential tweets with a link advising: "Get the facts about mail-in ballots." Critics say Trump thinks wider absentee voting will help Democrats and is signaling that he may challenge the Nov. 3 outcome if he doesn't win a second term. Experts says there's minimal evidence of meaningful fraud in mail-in voting, which they see as a vital part of conducting the 2020 general election safely and securely -- including for groups such as the elderly, who are more likely to vote for Republicans.

Five states (Colorado, Hawaii, Oregon, Utah and Washington) already vote almost entirely by mail, as do military members stationed away from home. "In my state, I'll bet 90 percent of us vote by mail," says Sen. Mitt Romney, R-Utah. "It works very very well and it's a very Republican state." Elsewhere, "much of the country is not ready for a surge of absentee voters," a recent Washington Post editorial says. "Serving millions of new absentee voters will be a massive logistical challenge for most states. . . . States and localities must buy letter-opening machines, mail sorters and ballot scanners. They will need space to accommodate equipment and staff practicing social distancing measures. They will need money for printing and postage."

Primaries in recent weeks have increasingly relied on mail ballots as voters consider the health risks of mingling with others and as some areas limit the number of polling places. In Wisconsin, more than 1 million absentee ballots were submitted for a statewide primary and special election in April. "There's no form of voting that is absolutely foolproof . . . but mail voting is very secure," says Wendy Weiser, director of the Democracy Program at New York University School of Law. "The rate of fraud is very small. It is very easy to get caught."

California official says: "Expanding vote-by-mail during a pandemic is not a partisan issue — it’s a moral imperative to protect voting rights and public safety. Vote-by-mail has been used safely . . . for years." – Alex Padilla, secretary of state

Republican leader says: California's "radical plan is a recipe for disaster that would create more opportunities for fraud and destroy the confidence Californians deserve to have in their elections." – Ronna McDaniel, Republican national chair