TODAY'S TOPIC is political déjà vu.

Pennsylvania's known for it. Same kinda stuff over and over. It even shows up in campaigns.

Take our April 26 Democratic U.S. Senate primary featuring Joe Sestak, Katie McGinty and John Fetterman.

If you're following at all you might be thinking, hey, wait, this feels familiar.

You're right.

It's not a total match with a past campaign, and Fetterman is certainly something new, but there are similarities between this race and the 2010 Democratic Senate primary, which also featured and was won by one Joe Sestak.

How's it similar?

Now, as then, Sestak's fighting against a strong current, which he is likely used to, given his 30-plus years in the Navy.

Now, as then, Sestak's not his party's favorite, which isn't at all surprising, given his go-my-own-way style.

And the 2010 Democratic establishment ditched Sestak in favor of then-incumbent Arlen Specter, who switched from Republican to Democrat and who the party figured was the better bet.

This year, despite the fact that Sestak beat Specter and only narrowly lost the general election to Pat Toomey in a Republican-dominated off-year contest, party powers also went for someone else, the aforementioned McGinty, who they figure is a better bet.

More similarities?

In 2010, Specter was endorsed by President Obama, Vice President Biden, Sen. Bob Casey, Senate Democratic leadership, Gov. Rendell, Mayor Nutter and many unions, including giants such as the AFL-CIO, SEIU and PSEA.

This year, McGinty is endorsed by President Obama, Vice President Biden, Sen. Bob Casey, Senate Democratic leadership, former Gov. Rendell, former Mayor Nutter and many unions, including giants such as the AFL-CIO, SEIU and PSEA.

I asked Christopher Nicholas, a GOP consultant who worked for Specter before and after Specter's party flip, for his thoughts on the Democratic establishment.

"I laud them for their consistency," he said.

But in 2010, the power backing didn't matter.

So the question is: Does history repeat itself, allowing twice-unwanted Sestak to win again? Or are there significant differences now favoring the favored McGinty?

Here's one difference.

Two weeks from primary day 2010 Sestak trailed Specter by eight points in public polls. Sestak won the race by seven points.

Two weeks from primary day 2016, Sestak leads McGinty by 10 points. Insiders say that it's McGinty who's closing; she might trail in polls to the end and still win the race.

Unless history repeats in another way.

Sestak beat Specter largely due to a Sestak TV ad by Philly-based The Campaign Group. The ad tied Specter to George W. Bush and Sarah Palin and included a video clip of Specter saying his party switch "will enable me to be reelected." The ad's tagline suggested the only job Specter cared about was his own.

This year, The Campaign Group is making TV spots for a super PAC, Accountable Leadership, backing Sestak. So we'll see.

There are other unknowns.

One is how Fetterman, a distant third in polls, impacts the vote. There were just two candidates in 2010. But now, in a year when unconventionality is drawing support (think Donald Trump and Bernie Sanders), who does Fetterman take votes from?

Then there's the impact of the presidential race. There wasn't one in 2010.

If Hillary Clinton vs. Sanders means higher-than-normal turnout, as is likely, who benefits? You'd think party-backed McGinty since primary voters tend to be hardcore party folks. Ah, but Sanders voters are not. And that could boost Sestak or Fetterman (who endorsed Sanders and expects to campaign with him).

Two things are certain: Tons of money poured in by the national party, unions and interest groups such as Emily's List will be spent for McGinty; and since she's currently trailing Sestak she'll go at him in TV spots to knock his numbers down.

What's uncertain is whether that sinks Sestak or whether he stays on course - to the isle of déjà vu.