Whatever the outcome of Tuesday’s tight congressional contest in Tampa Bay, this footnote is assured: The winner will become the 64th person in the current House first sent to the Capitol by a special election. That’s an astonishing 15 percent of the membership.  

Florida’s contest between Democrat Alex Sink and Republican David Jolly  is the year’s first valid test of midterm voter sentiment, but at the historical edges it’s something more: an opportunity to see whether women and Democrats continue their run of good fortune when the voters go to the polls in between the even-numbered Novembers.  

The campaign in suburban St. Petersburg, a swing district held for four decades by the late GOP Rep. C.W. Bill Young, has encapsulated themes that look to remain prominent across the country for the next eight months. Jolly, a lobbyist and former top aide to Young, would portray his win as a repudiation of the 2010 health care law and the Obama administration agenda. Sink, a former chief financial officer for Florida, would portray her victory as a rejection of conservative efforts to curb Social Security and otherwise rend the social safety net.  

And the losing party is sure to downplay the result and insist the election is not a national harbinger, while clamoring to improve its positioning for the contest for the very same seat in November.  

Recent history suggests that task would be an uphill climb: 85 percent of special-election winners so far in the 21st century have won at least two subsequent general elections. (Only six have been turned away after such short careers, most recently a pair of Democrats in 2012 whose districts were significantly redrawn after their initial arrivals: Kathy Hochul, who represented upstate New York for 19 months, and Mark Critz, who held his southwestern Pennsylvania seat for one term and seven months.) Although the Florida race has remained a tossup to the very end , despite a combined $9 million in campaign spending over the past five months, the curious statistics about special-election survivors offer the Democrats something of a good omen.  

Based on her party as well as her gender, the numbers give Sink an edge. One in 5 members of the House Democratic Caucus was first chosen in a special election, compared to just 1 in 10 House Republicans. And female candidates have proved twice as successful getting to Congress in specials than by running in the regular biennial cycle.  

The 38 Democrats who arrived after a special include not only the retiring dean of the House, John D. Dingell of Michigan, who succeeded his late father in 1955, but also the party’s top two leaders: Minority Leader Nancy Pelosi won the San Francisco seat opened by the 1987 death of Democrat Sala Burton, and six years earlier Minority Whip Steny H. Hoyer won a Maryland seat declared vacant because of the incapacitation of Democrat Gladys Noon Spellman.  

The 25 Republicans who won their seats in specials include three current committee chairmen — Oklahoma’s Frank D. Lucas of Agriculture, Pennsylvania’s Bill Shuster of Transportation and Infrastructure and Florida’s Jeff Miller of Veterans’ Affairs — and the most senior member of the caucus, Don Young of Alaska. (He was sworn in 41 years ago last week to succeed Democrat Nick Begich, father of the state’s junior senator, whose campaign plane disappeared in October 1972.)  

A review of modern congressional history offers no easy rationale for why the House’s current “special election caucus” is disproportionately Democratic — except for the truism that more reliably Democratic seats have come open at odd times in recent decades because of deaths, resignations or promotions.  

What’s more vexing to explain is the outsized strength of women in such campaigns. While they have won only 11 percent of House general elections since 1980, they have triumphed in 24 percent of the 141 special elections in that time, according to a study released last weekend by Eric J. Ostermeier of the University of Minnesota’s Humphrey School of Public Affairs. In the past decade, the success rate for women in specials has jumped to 33 percent, even as their percentage of November victories peaked at 18 percent in 2012.  

“There’s a big enough sample size here that this is not some random result. Something’s going on to benefit women in special elections, I just can’t pinpoint that cause,” Ostermeier conceded Monday.  

A bit easier to explain, he said, is why each of the last dozen women to win a special election has been a Democrat. (The most recent was Katherine M. Clark of Massachusetts in December) while only two GOP women have won specials in this century. (Shelley Sekula Gibbs of Texas served just seven weeks in 2006 and Jean Schmidt of Ohio lost her 2012 primary for a fourth full term.)  

The “widow’s mandate ” — the ticket to Congress for a deceased lawmaker’s spouse often awarded in the last century — has now been more or less supplanted by nominees being chosen on their own merits. And the Democrats, with a much deeper bench of female state and local officials, have been more prepared to capitalize on the long-lasting partisan gender gap by nominating women for these mid-session vacancies.  

Three more special elections are already in the offing this year, and women look to be serious players in two. State Rep. Alma Adams is in the top tier of Democrats in North Carolina vying to replace Melvin Watt, now the federal housing administrator. And state Senate Majority Leader Lizbeth Benacquisto is one of the leading candidates for the GOP nomination to succeed the recently resigned Trey Radel in Florida.  

Neither of those specials offers the sort of bellwether test for national themes that’s happening Tuesday because Watt’s old seat is solidly Democratic and Radel’s former district is reliably Republican. But the awarding of the nominations — April 22 in Florida and July 15 in North Carolina — is an opportunity to see the power of gender in this slice of American political life.  

Editor’s note: Due to a copy editing error, an earlier version of this column incorrectly identified the Florida special election as taking place in the city of Tampa. It is in the Tampa Bay region, but the city does not fall within the 13th District.