The man who helped invent scratch-off lottery tickets now has his sights set on a bigger prize: overhauling the way the United States elects presidents.

On Tuesday, Nevada became the latest state to pass a bill that would grant its electoral votes to whoever wins the popular vote across the country, not just in Nevada. The movement is the brainchild of John Koza, a co-founder of National Popular Vote, an organization that is working to eliminate the influence of the Electoral College.

If Nevada’s governor signs the bill, the state will become the 15th — plus the District of Columbia — to join an interstate pact of states promising to switch to the new system. Those states, including Nevada, have a total of 195 electoral votes. The pact would take effect once enough states have joined to guarantee the national winner 270 electoral votes, ensuring election.

Enforcement, however, could be very difficult without congressional approval, according to constitutional law experts. And the pact would be highly vulnerable to legal challenges, they say.