In the most hotly contested House race of 2014, the candidates don't matter.

We're talking about Florida's 13th district special election, in which Democrat Alex Sink and Republican David Jolly have run lackluster campaigns against the backdrop of millions of dollars in outside spending that has upstaged them. This is precisely why Tuesday's outcome means so much to national Democrats and Republicans: It's the purest test yet of broad messaging and tactics both sides hope to deploy in the fall midterms.

As we've often written in this space, candidates do matter. Florida's 13th district is the exception because of how the race has unfolded.

Jolly's a former lobbyist who has struggled to raise money. He irked Republicans by criticizing the air cover they have given him in the form of anti-Sink ads. His positive message has been drowned by an expensive air war on issues like health care and Social Security. Sink is strong fundraiser but has veered off message at times and maintained a low profile in the final stage of the race.

In other words, if Jolly wins, it's not going to be because his strengths as a candidate propelled him across the finish line. Ditto for Sink. Polls show a very tight race.

It's not that the candidates don't matter at all. Fundraising is a big part of running for office. If Jolly had raised more money to blanket the airwaves with positive ads after the GOP primary, he'd probably be better off right now. The Post's Paul Kane reported from the district that Jolly said "the unfortunate thing is I’m not sure the voters know exactly where we stand on the issues."

But he didn't, leaving GOP outside groups to take the lead in spending on television, mail and other modes of communication. Much of their advertising has focused on slamming Sink for supporting the federal health-care law. Republicans hope to replicate the same tactic in dozens of other competitive congressional races this fall.

Even as Sink raised lots of money (at least $2.7 million in under four months), Democratic groups have poured in millions more to play a major role in the messaging battle. These allies have spent some $3.75 million hitting Jolly or supporting Sink, an analysis from the Center For Responsive Politics shows. Democratic ads have slammed Jolly for wanting to repeal the health-care law, a message the party is test driving ahead of the fall campaign.

Not only are outside groups driving the narrative -- they are driving the narrative in a swing district. President Obama narrowly won the 13th district in 2012. But it was represented by Republican C.W. Bill Young for decades.

The 13th is not a demographic microcosm of the country. Its residents are older than most other districts. That presents Democrats with a challenge, as older votes tend to vote Republican. Public polling has shown an electorate that would tilt between 8 and 13 percentage points toward the GOP. And Republicans have returned more absentee ballots than Democrats. Voting by absentee is the dominant way of casting ballots in the district.

But it's a toss-up race nonetheless. Sink has more crossover appeal, and the Republican voters in the 13th tend to be moderate and are very winnable for a Democrat. It's not a tea party crowd.

No special election is a perfect barometer of anything. Many are over-hyped as harbingers of something. But Florida's 13th district is as good a test of overarching GOP and Democratic strategies as we have seen in quite a while.

And it's not because of Jolly or Sink.