David Perdue took the cheap and easy route.

The Republican Senate candidate in Georgia, like Republican candidates in most other competitive races, calculated that the surest road to victory was to tie his opponent, in this case Democrat Michelle Nunn, to President Obama.

“The president himself said, ‘make no mistake, these policies are on the ballot,’” Perdue said in a TV ad last week. As a photo of Obama with Nunn filled the screen, Perdue continued: “That’s why he wants her in the Senate.”

It was typical of Perdue’s campaign strategy of trying to run against Obama. What was not typical was Nunn’s response: She ran a spot of her own, featuring the same photo of herself with Obama.

“Have you seen this picture?” she asks viewers. “It’s the one David Perdue has used to try and attack me in this campaign.” As the image shifts to a photo of George H.W. Bush with his hand on her shoulder, Nunn goes on: “But what he doesn’t tell you is that it was taken at an event honoring President Bush, who I worked for as CEO of his Points of Light Foundation. Throughout my career I’ve been able to work with Republicans and Democrats, and that’s the same approach I’ll bring to the U.S. Senate.”

Nunn, daughter of the legendary Senate Democratic centrist Sam Nunn, may yet lose the race. But she is doing far better than expected in her run despite the hostile year and terrain for Democrats. A big reason for this: She’s showing authenticity and courage at a time when both are in short supply among Democratic candidates.

Nunn’s comfort in her own skin is in sharp contrast to other Democrats on the ballot, who are making awkward maneuvers to distance themselves from Obama and much of the Democratic Party.

In Kentucky, Democratic Senate candidate Alison Lundergan Grimes ran an ad declaring “I’m not Barack Obama.” In Louisiana, an ad from Democratic Sen. Mary Landrieu showed her saying “the administration’s policies are simply wrong on oil and gas production.”

Sen. Mark Begich (D-Alaska) boasted in an ad that he “took on Obama” on Arctic oil production and “voted against President Obama’s trillion-dollar tax increase.” (Actually, the vote was a Republican stunt.) Sen. Mark Pryor (D-Ark.) bragged of opposing gun restrictions Obama favored, proclaiming, “No one from New York or Washington tells me what to do.”

And then there’s Sen. Mark Udall (D-Colo.) who skipped an Obama visit to his state and made the absurd claim that, at the White House, “the last person they want to see coming is me.”

But running from Obama is dumb, both because it doesn’t fool anybody and because it makes the candidate look shifty. Certainly, Obama is unpopular in the states that form this year’s battlefield. But voters are savvy enough to know that Democratic lawmakers tend to support a Democratic president. And Obama seems to have a suicidal wish to remind Americans of this, telling liberal radio host Al Sharpton Monday that “these are all folks who vote with me.”

The attempt to run from Obama only makes the runner look calculating at a time when voters are disgusted with anything that smells political. That helps to explain the Elizabeth Warren phenomenon. The Democratic senator from Massachusetts, a raging populist, is far more liberal than Obama. Yet she’s in demand as a surrogate for Democrats even in places such as Kentucky and West Virginia.

As The Post’s Paul Kane noted, she’s campaigning for Senate candidates in Minnesota, Iowa and Colorado this week, and candidates are clearly not afraid to stand with her as she delivers her fist-pumping jeremiad against Republicans and wealthy interests.

Contrast that with Kentucky’s Grimes, who had a promising start but has turned into a feckless candidate. She repeatedly refused to say whether she even voted for Obama, actually claiming during a debate last week that she wouldn’t “compromise a constitutional right” by revealing this secret.

The day after that preposterous dodge, the Democratic Senatorial Campaign Committee said it was stopping advertising in Kentucky — essentially an acknowledgment that Grimes would lose — and was buying advertising time in support of Nunn in Georgia.

Republicans tried to play the same game with Nunn, but she didn’t make Grimes’s mistake. “I did vote for the president,” she told The Post’s Ed O’Keefe.

Of course she did. She’s a Democrat, and she’s not going to insult voters’ intelligence by pretending otherwise. If that causes her to lose in Georgia, she at least will have kept her dignity.

Twitter: @Milbank

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