Cook Political Report on Wednesday said Clinton had 64,225,863 votes compared to Trump's 62,210,612 votes.
Clinton's victory in the popular vote has generated criticism against the United States' Electoral College system. Some activists and academics that formed a coalition are calling on U.S. authorities to fully audit or recount the election results, particularly in Michigan, Pennsylvania and Wisconsin.
The coalition hopes Clinton's campaign will join its efforts as it prepares to deliver a report of its concerns to congressional committee chairs and federal authorities next week.
"I'm interested in verifying the vote," Dr. Barbara Simons, an adviser to the U.S. election assistance commission and expert on electronic voting, told The Guardian. "We need to have post-election ballot audits."
Following the 2016 election, Clinton's loss is the fifth time in U.S. history a candidate who won the popular vote did not assume the presidency. The last time was in 2000, when former Vice President Al Gore defeated then-Texas Gov. George W. Bush in the popular vote, but lost the recount in Florida -- giving Bush the needed electoral votes to win the executive branch.
Since his election victory, Trump has defended the Electoral College, despite calling the system a "disaster for a democracy" in 2012.