For decades, liberals have created a caricature of Republicans as being more about bombast and white resentment than substance and principles. Should Donald Trump win the GOP presidential nomination, it would help validate this cartoonish portrait.

That's why those who work to elect Republicans and advance conservative policy ideas are recoiling from his dominance in polling. It's why liberals are greeting his rise with "I told you sos" and why their allies in the media are perfectly content to promote Trump and allow him to define the GOP electorate.

Every Republican electoral victory from Richard Nixon's in 1968 to the GOP's 2014 landslide has been portrayed by the Left as the rebellion of the Angry White Male. In liberals telling, every conservative policy, from reducing spending to cutting taxes, is rooted in racism.

Democrats tried to dismiss Ronald Reagan — the twice-elected governor of the nation's largest state who had been articulating his domestic and foreign policy worldview for decades — as a personality rather than substantive leader. To this day, liberals like to say that Republicans are nihilists who have no interest in actual policymaking.

To Republicans and conservatives who got involved in politics to advance a set of ideas — the type of people who get their kicks debating the finer points of tax policy, national security, and Commerce Clause jurisprudence — this liberal caricature has seemed utterly bizarre and intentionally dishonest.

But in Trump, liberals have finally found a Republican candidate who embodies everything they've been saying about the party's voters all along.

So far, Trump's candidacy has been bookended by attacks on Mexicans for being rapists and a proposal to ban a religious group from entering the United States — with insults against women and the disabled sprinkled in between.

Trump is a white male pushing 70 who inherited wealth, manipulated bankruptcy law, and relied on crony capitalism in his business dealings.

His life has been a reality show since before reality TV formally existed. His campaign has been more about flash than substance. He hasn't waded too deeply into policy beyond provocative statements and boasts that every national and international problem can be cured by his sheer awesomeness. To the extent that he has outlined a policy vision, it's been incoherent and largely unworkable.

He has a weak record on all the issues that matter to ideological conservatives. At various times he's backed tax hikes, socialized medicine, farm subsidies, abortion, and government seizures of private property. In an era when Republican primaries are dominated by news of the ideological deviations of all the candidates, Trump's supporters have shrugged his embrace of big government and even of Democratic politicians.

This has delighted liberals, who now feel vindicated. And it has rankled establishment Republicans and professional conservatives.

Establishment Republicans who are focused on winning elections have absorbed data on the changing face of the American electorate and shudder at the thought of what a Trump candidacy would mean not only to their prospects of retaking the White House, but of maintaining their Senate majority and branding the GOP as a party welcoming to minority groups and younger voters.

But beyond the establishment Republicans, there are professional conservatives — who I'd define as conservative commentators, think tank analysts, and activists — who are committed to advancing a conservative policy agenda, often putting them at odds with the GOP establishment. They're also largely anti-Trump, and wince at the prospect of a Republican nominee who has steadfastly rejected limited government conservatism.

These Republicans and conservatives dread the idea of liberals, for years, being able to throw Trump back in their faces every time they explain that conservatism is really about reforming and shrinking the federal government so its size and scope is closer to its constitutionally limited role. The idea of Trump as the nominee will overpower polling evidence that his support is not coming from ideological conservatives.

Should Trump lose Iowa and collapse thereafter, his foray into presidential politics will likely end up being more associated in the public consciousness with his brand and ongoing celebrity saga than with the Republican Party. But should Trump start winning primaries and eventually capture the nomination, he will do lasting damage to the image of Republicans and conservatives.