How many of us have heard that a vote for a third party is a vote for Hillary?

Apparently, that goes both ways.

Democrats are charging that a vote for Gary Johnson is actually a vote for Donald Trump, and they’re looking to eliminate that particular burr from under their saddle.

Liberal groups are passing around embarrassing videos of Johnson and running ads against him warning about his positions on issues like climate change that are important to young voters and independents.

The Clinton campaign will rely heavily on Sen. Bernie Sanders (I-Vt.) in the coming weeks as it seeks to shore up its deficit among young voters and left-leaning independents who are not energized by her campaign and are considering casting a vote for either Johnson or Green Party nominee Jill Stein.

I guess perspective is everything, isn’t it?

It’s the youth vote that has largely fueled the engine of the Johnson/Weld ticket. They are finding it easier to relate to Johnson than a hedonistic septuagenarian or a sickly, plastic grandma.

NextGen Climate, the group run by liberal billionaire and environmental activist Tom Steyer, is on the ground in eight battleground states with a message that is almost exclusively aimed at reaching the millennial voters who are energized by the issue of climate change.

Last week, the group threw six figures behind digital ads mocking Johnson as a climate change denier and warning millennials that climate change will cost them trillions of dollars.

A source at NextGen told The Hill the group will be looking to turn out young voters for Hillary Clinton and down-ballot Democrats with a texting campaign in the battleground states and a carpooling service that will drive them to the polls.

It’s a clever ploy… until the carpooling service gets them to the polls and they vote for Johnson, anyway.

Liberals are also hoping that the brand of celebrities can be used to persuade young voters to abandon the notion of a third party vote, in favor of Hillary.

Cher, George Takei, Seth McFarlane, and a host of liberal writers are putting their two cents worth into the effort, as well.

“I’d like to make a plea to young Americans: your vote matters, so please take it seriously,” Paul Krugman wrote in a Libertarian takedown in The New York Times last week.

Yeah, sorry Paul. I imagine that with the exception of Seth McFarlane, most of today’s youthful voters have no idea who you or the others are, or at least, don’t care.

It’s highly unlikely that either Johnson or Green Party candidate, Jill Stein will get close enough to take down either Clinton or Trump, but the votes they do manage to pull away could alter the outcome of the race.

A CNN-ORC survey that showed Trump with a 1-point edge in Colorado found Johnson and Stein combining for 30 percent support among those under the age of 45.

In Monmouth University polls of Nevada, Clinton once had a 5-point lead over Trump based on her strength among independents. The latest survey found Trump moving into a 2-point lead as independents moved away from Clinton into Johnson’s column.

And one eye-popping Christopher Newport University survey of Virginia found Clinton taking 34 percent among voters aged 18 to 34, followed closely by Johnson at 27 percent. Clinton still leads by 6 over Trump in that poll but only pulls 39 percent support overall.

The real problem here is the attitude that Democrats have that they’re “owed” the youth vote. This is the same attitude that tells them they’re “owed” the minority vote, or “owed” the female vote.

They’re not in full panic mode, yet, but as we get closer to November, expect them to turn up the heat and get a bit more aggressive with those groups who aren’t falling in line with the liberal Democrat vision for their futures.