President Donald Trump pressed the notion of widespread voter fraud again, despite a continued lack of evidence to back up those claims.

Trump tweeted Wednesday morning:

I will be asking for a major investigation into VOTER FRAUD, including those registered to vote in two states, those who are illegal and....

even, those registered to vote who are dead (and many for a long time). Depending on results, we will strengthen up voting procedures!

White House Press Secretary Sean Spicer on Tuesday said: "[Trump] has stated his concerns of voter fraud and people voting illegally during the campaign and continues to maintain that belief based on studies and evidence people have presented to him."

The president's belief that millions of people voted illegally in the 2016 presidential election costing him the popular vote has been widely challenged.

In court filings last year in the effort to block recount efforts by Green Party candidate Jill Stein, attorneys for Trump wrote: "All available evidence suggests that the 2016 general election was not tainted by fraud or mistake," according to The Washington Post.

Trump also tweeted on Wednesday morning a timetable for his Supreme Court nominee announcement to fill the vacancy on the nation's highest court created by last year's death of conservative Justice Antonin Scalia.

I will be making my Supreme Court pick on Thursday of next week.Thank you!

The leading contenders, according to a person who spoke to the Associated Press anonymously, are judges William Pryor, Neil Gorsuch and Thomas Hardiman.

Senate Republicans prevented then-President Barack Obama from filling the seat, a political gamble that paid off when Trump was elected.

Correction: This story was revised to delete an outdated reference to Trump's status.