White House spokesman Sean Spicer could not offer specific evidence Tuesday to support President Donald Trump's unsubstantiated claim that he lost the popular vote because millions of people voted illegally.

The president has repeatedly defended his popular vote loss since the November contest and did so again in a Monday meeting with congressional leaders, according to NBC News. Trump spent about 10 minutes of the bipartisan meeting talking about how 3 million to 5 million "illegals" voted, costing him the popular vote.

Trump has presented no specific evidence to back that claim, and state election officials have said they did not see widespread voter fraud. House Speaker Paul Ryan said Tuesday that he has seen "no evidence" to back Trump's argument.

Spicer said Tuesday that Trump has long held that belief "based on studies and information he has." When pressed more than once on Trump's evidence, he cited a 2008 Pew study that detailed millions of out-of-date voter registrations due to people dying or moving out of a state.

However, the Pew study did not say that the registration errors led to illegal voting.

Spicer said that the Trump administration will "maybe" consider an investigation into illegal voting allegations. Spicer added that Trump is "very comfortable with his win" despite his repeated justifications for his popular vote loss.

Trump's unsubstantiated voter fraud arguments have led to concerns that he will use them to justify laws that restrict ballot access.

