California is already on defense in its battle with Donald Trump.

We need offense—now.

Trump is attacking our state as if it were just another political opponent. His strategy is not merely to punish California; he wants to rob our state of its political legitimacy.

So the president of the United States has falsely claimed that California’s elections are fraudulent exercises involving millions of illegal votes. He’s frequently accused our biggest cities of endangering our country by failing to assist with deportations. He has called California “out of control” and threatened to “defund” state programs.

Such attacks are so potentially damaging (since California is the world’s sixth-largest economy and a vital model of diverse peoples prospering together) that we need to fight back much more directly.

Put simply, California must delegitimize Trump before he delegitimizes us.

There are two ways to go on offense. First, Californians should aggressively question Trump’s legitimacy as president. Second, we must bolster our state’s own legitimacy by reaching out to the rest of America and reaffirming how proud we are to be a part of this country.

Any outrageous allegation Trump makes against us should be answered with greater outrage. If Trump wants to invent claims of fraud in our elections, we should target his own frauds—from his business dealings to Trump University. When Trump threatens the funds for state programs, Californians should point out that Trump’s budget and tax plans could bankrupt the whole country.

And when Trump alleges that California is “out of control,” California should press the president on those who control him. Why bother negotiating energy policy with you, Mr. President, when we can go to the Kremlin or Goldman Sachs, the real powers behind your false throne?

The most powerful line of attack against this president is to question his loyalty to the country. Trump has billed himself as an unapologetic nationalist, vowing to make America great again. But he’s deeply vulnerable on nationalist grounds. He constantly slanders the country—from lying about the murder rate to equating America’s leaders with the murderous Vladimir Putin. Californians must convince our fellow citizens that Trump’s attacks on this most American of states are an attack against our entire country.

To emphasize Trump’s lack of patriotism, we Californians should put our American patriotism on full throttle. While Trump denigrates America on Twitter, California leaders should be meeting with counterparts across the country, looking for areas of cooperation. When another state faces emergency, California should be the first to send help. And whenever another state celebrates a great triumph, our leaders should congratulate them in person.

In reaching out, especially to Republicans, we should deploy the words of California’s “great communicator”—Ronald Reagan—as weapons against the current president. To explain our fight with Trump: “When you can’t make them see the light, make them feel the heat.” To explain our protests: “No weapon in the arsenals of the world… is so formidable as the will and moral courage of free men and women.”

California also should make a point of reaching out to U.S. allies Trump is offending. Governor Brown should convene summits with the leaders of Mexico (we could go on offense by opposing not only Trump’s wall but the existing border barrier, an eyesore that inconveniences tourism and commerce), Canada, Australia and Germany, and sign environmental, trade and tourism agreements with them. Then we could ask: Why doesn’t the president make deals like that?

Sun Tzu advised, “If your opponent is of choleric temper, seek to irritate him.” This offensive strategy—reaching out to Americans while attacking Trump’s legitimacy—would irritate and isolate him. That’s the best way to weaken Trump—and protect our state and our country.

Joe Mathews writes the Connecting California column for Zócalo Public Square.