Top Republicans are taking Pete Buttigieg seriously as a potential general election candidate after his breakout poll in Iowa. The respected Des Moines Register poll, released Saturday night, has Buttigieg at the top of the Democratic pack in Iowa.

What they're saying: "He'd be a fresh face with a message of unity and a more traditional Democratic program that's not as scary to suburbanites," Karl Rove told me. "His weaknesses would be in motivating African Americans and connecting with blue-collar middle America that's dubious of any Harvard-educated elites."

Others, including several top Trump advisers, raised concerns that Buttigieg is more talented than Joe Biden and that he will be harder to brand as a leftist radical than Sens. Elizabeth Warren or Bernie Sanders.

"Buttigieg might be better for them to win Wisconsin than Warren," said a source close to the Trump campaign. "And I think it comes down to Wisconsin right now."

Buttigieg, the 37-year-old mayor of Indiana’s fourth-largest city, has defended himself against charges of inexperience by saying he has more executive experience than Trump.

But he's failed, so far, to win support from many African American voters. And some of his outreach efforts have backfired badly. The Intercept's Ryan Grim published a damaging story on the blowback to Buttigieg's poorly handled plan to gain support from black voters in South Carolina.

A Buttigieg spokesperson said: "Pete believes we need to dismantle systemic racism in order to deliver justice for Black Americans and make our country whole. Which is why, as we said the time of its release, we're proud the Douglass plan has earned the support of many South Carolinians, including many African-Americans," per The Intercept.

What's next: Buttigieg has had a huge surge of support in Iowa, but he has never had to face the scrutiny and attacks that come with frontrunner status. This week, that will likely change. Watch for the other candidates to turn on him in Wednesday's Democratic debate in Atlanta.

Go deeper: Buttigieg with 9-point lead in new Iowa poll