Democratic presidential candidate, former Vice President Joe Biden holds his notes as he speaks to members of the clergy and…
Democratic presidential candidate, former Vice President Joe Biden holds his notes as he speaks to members of the clergy and community leaders at Bethel AME Church in Wilmington, Del., June 1, 2020.

WASHINGTON - June 2 was supposed to be the finish line for what seemed like an endless 2020 U.S. presidential primary campaign. In most election years, a party’s nominee for president of the United States is locked up by then.    

For the last 33 months, 33 people campaigned for the Democratic nomination for president. The June 2 primary states could possibly crown a nominee.  

But then the coronavirus pandemic hit and dramatically scrambled the campaign calendar.    

In mid-March, states started to postpone their primary elections to prevent crowds at voting places and to buy time to expand vote-by-mail opportunities.   

Montana, New Jersey, New Mexico, South Dakota and the District of Columbia were already scheduled to hold primary elections Tuesday.  

However, in an effort to contain the spread of the coronavirus, six other states postponed their primaries until June 2 — making it the second biggest day for selecting delegates behind “Super Tuesday” held March, 3 when roughly a third of all the delegates to the Democratic national convention were chosen.  

Indiana, Maryland, Pennsylvania and Rhode Island moved their primaries to Tuesday. Two states further postponed their primaries -- Delaware to July 7 and Connecticut to August 11.

WATCH: Tuesday primary elections

Former Vice President Joe Biden is the presumptive Democratic nominee who has an outside chance of locking up the nomination next Tuesday, reaching the golden number of 1,991 delegates. Biden currently leads Vermont Sen. Bernie Sanders in delegates 1,150 to 860, according to a CBS News count.  

Sanders dropped out of the race in early April and threw his support behind Biden when it became obvious Biden held an insurmountable lead. But Sanders kept his name on the ballot to enhance his influence at the national convention in drafting a platform.  

Biden will likely sweep most of the remaining primaries and all the pledged convention delegates, but he technically may not quite lock up the nomination for a while longer. In the meantime, many states are looking to shift to voting by mail in the remaining primary elections and the November general election, despite President Donald Trump’s claim that voting by mail fosters fraud.

Voters drop off ballots in the Washington State primary, March 10, 2020 in Seattle.

Currently, five states hold elections by mail only. Most of the other states allow voters to request an absentee ballot without needing an excuse, such as military duty, disability or being away from home on Election Day.    

A few states still require a valid excuse and are not making an exception for the coronavirus.  

Steven Mulroy, a University of Memphis law professor who represents several voters, is suing the governor of Tennessee to loosen absentee ballot requirements.  

“It is an unreasonable burden on our fundamental right to vote to require that we vote in person when we know that congregating with others in person creates a significant risk of infection and then transmission of the disease to other people, many of whom will have underlying conditions that make them particularly vulnerable,” Mulroy said.     

Idaho was among 13 states that moved their primaries to June 2 or beyond. The state decided to conduct the primary by mail only. More than 400,000 people — 47% of Idaho’s registered voters —- asked for absentee ballots, an “unprecedented response,” according to the secretary of state’s office.    

The deadline for Idaho voters to turn in their ballots is June 2.