With President-elect Donald Trump’s share of the popular vote falling further and further behind Hillary Clinton’s, Sen. Bernie Sanders (I-Vt.) says it may be time to consider changing the Electoral College system that gave Trump his victory last week.

“We may want to take a look at the whole Electoral College, which is seating a man for president who didn’t get the most votes,” said Sanders in an interview with USA Today. “This is something we need a serious discussion on. This campaign revolved around 15 states of the country, right? Battleground states. My state of Vermont is a strong Democratic state; no one paid attention. Wyoming is a Republican state; nobody paid attention to Wyoming. Is that a good way?”

Current popular vote counts show Clinton leading Trump by more than 750,000 votes. With election officials still tallying provisional, mail-in and absentee ballots, particularly in heavily blue states, many expect Clinton’s margin of victory in total votes to increase in the coming days, perhaps to as much as 2 million.

But thanks to the Electoral College, none of this kept Trump from securing a comfortable win on Tuesday. For the second time in the last 20 years, a Republican candidate is headed to the White House with fewer votes than his Democratic opponent.

The Constitution’s framers came up with the idea of the Electoral College to ensure that no state had too much power in deciding presidential contests. But due to racial and geographic breakdowns, the system now gives disproportionate power to rural white voters, who are more likely to live in competitive battleground states, while people of color tend to be over-represented in safely blue or red states.

As Sanders points out, presidential candidates typically campaign with this in mind, focusing only on a handful of states they need to swing in order to collect 270 Electoral College votes. Candidates rarely visit Democratic or Republican strongholds, like the comfortably blue California or reliably red Texas.

“I think we want to rethink that,” Sanders told USA Today.

Trump’s win has reignited debate about abolishing the Electoral College in favor of a format centered on the results of the popular vote. A MoveOn petition toward this goal now has nearly 500,000 signatures.

To drop the Electoral College, the U.S. would have to pass a constitutional amendment. This process typically requires two-thirds of the House and Senate to vote on a proposal, which 38 states must then ratify.

In an interview with Bill Maher on Friday, former U.S. Attorney General Eric Holder said the latest election is proof it’s time to begin that campaign in earnest.

“All right, it involves heavy lifting. Let’s lift heavy, let’s do it,” said Holder.