0/10 In my book "Rigged," I unearth the history of covert electoral interference, and I argue that the lessons of the past can and must be used to protect our democracy now.

Here are ten historical lessons that should inform our response to the threat of foreign interference:

1/10 Covert electoral interference has always involved efforts to change actual votes and efforts to change minds. The latter is far more common than the former, and America must address both.

2/10 It has never been possible to determine the precise impact of operations to change minds. This unanswerable question of effectiveness should not be used to dismiss the threat of covert electoral interference.

3/10 Some politicians have historically embraced foreign interference on their behalf, while others have rejected it outright. Leaders who prioritize their countries’ sovereignty fall into the latter category.

4/10 Revelations of foreign operations to influence elections once outraged Americans on both sides of the aisle. This should again be the case today.

5/10 Moscow has long channeled its strategic priorities into its electoral operations. The Soviet Union backed Communist candidates; Putin will continue to back authoritarian-minded and disruptive ones.

6/10 Interfering actors adapt to the information environments of the moment. Cold War–era operations targeted radio and television; modern operations will target social media platforms and whatever conduit for propaganda emerges next.

7/10 Preexisting societal divisions present opportunities for interfering actors. The more polarized a democracy, the more vulnerable it is to foreign subversion.

8/10 Covert electoral interference is a global phenomenon. The simplest way to anticipate how Russia will interfere in America’s next election is to monitor how it is interfering in elections overseas.

9/10 No silver bullet will secure America’s elections. Lenin and Putin were right: Competitive elections are by nature penetrable. They always have been, and they always will be.

10/10 The digital age has universalized the threat of covert electoral interference. In the 20th century, no external actor could meaningfully manipulate U.S. elections. The internet has upended this dynamic. The U.S. is now as vulnerable as any democracy to foreign interference.