Larry Lessig, a Harvard University constitutional law professor who made a brief run for the 2016 Democratic presidential nomination, claimed Tuesday that 20 Republican members of the Electoral College are considering voting against Donald Trump, a figure that would put anti-Trump activists more than halfway toward stalling Trump’s election.

Lessig’s anti-Trump group, “Electors Trust,” has been offering pro bono legal counsel to Republican presidential electors considering ditching Trump and has been acting as a clearinghouse for electors to privately communicate their intentions.

“Obviously, whether an elector ultimately votes his or her conscience will depend in part upon whether there are enough doing the same. We now believe there are more than half the number needed to change the result seriously considering making that vote,” Lessig said.

Lessig’s claims contradict the assertions of Republican National Committee sources who report that a GOP whip operation intended to ensure Republican electors remain loyal to Trump found only one elector — Chris Suprun of Texas — would defy Trump.

Suprun is the only Republican elector to publicly declare his intention to cast a vote for someone other than Trump.

Lessig provided no evidence to back up his claim, but says his group has heard from 20 Republicans open to breaking with Trump. It’s unclear whether any of these potential anti-Trump GOP electors reside in states with laws that force them to vote for Trump or else be replaced by a pro-Trump alternate. Though similar laws are being challenged in court, it’s also unclear whether any Republicans in those states who vote against Trump would be counted.

The 538 members of the Electoral College – 306 Republicans and 232 Democrats – will gather in their state capitals on Dec. 19 and cast the official vote for president. If all Republican electors support Trump, he’d easily clear the 270-vote threshold he needs to become president. That’s why anti-Trump activists are lobbying to convince 37 Republicans to rebel against Trump.

The most electors to ever reject a presidential nominee occurred in 1808, when six Democratic-Republican electors rejected James Madison. There hasn’t been more than one so-called “faithless” elector in a single Electoral College vote for president since 1832, when two Maryland electors abstained.