For decades, the Republican Party in Philadelphia has willingly taken a back seat to the Democratic Party, in return for two reserved (and ineffective) seats on City Council, the right to mismanage the Parking Authority, city contracts, and some patronage jobs.

In return for its guaranteed sliver of the city’s spoils, the Philadelphia GOP — chaired by Michael Meehan and controlled for three generations mainly by his family — rarely nominates serious challengers for public office. The GOP’s willingness to let Democrats win citywide races is akin to how the Washington Generals roll over for the Harlem Globetrotters.

That brings us to the Republican candidate for mayor this year. Earlier this month, the city’s GOP ward leaders endorsed Daphne Goggins.

Goggins, 56, is the first African American woman the GOP has backed for mayor. Unfortunately, the rest of her resume is lacking. The North Philadelphia ward leader is unemployed and has been collecting disability since 2010.

In an interview last week with the Daily Caller, a conservative website, Goggins said she was bipolar and suffered from depression and anxiety. She said her disability is caused by “mental illness,” which surfaced after she stopped snorting cocaine in 2005.

If elected, Goggins said she could transition from collecting disability to the daily grind of being mayor because, as she explained, her cabinet would do most of the work.

No disrespect to Goggins, who apparently is an active community volunteer, but is this really the best candidate the GOP could find for mayor of the sixth largest city in America? More to the point, why is it that come nearly every city election, the Philadelphia GOP seemingly takes a dive?

After all, the Democratic Party in Philadelphia is hardly a model of good government. Just last month, City Councilman Bobby Henon became the latest in a long line of Philadelphia Democrats who have been indicted. Henon was charged with bribery, conspiracy, and fraud along with electricians’ union IBEW Local 98 boss John J. “Johnny Doc” Dougherty, who is credited with helping to elect Mayor Kenney and other Democrats.

Under Kenney, city spending has increased by $600 million in three years, while the pension system remains severely underfunded. Shootings were up 12 percent last year, while the number of murders hit a 10-year high, even as the murder rate declined in other large cities.

Such issues could make Kenney ripe for a reelection challenge. But the GOP’s lack of effort usually means mayors sail to reelection. Same goes for City Council members who rarely face serious challengers.

Such complacency helps explain why DROP continues to drain city coffers and why Philadelphia has one of the highest overall tax burdens in the country and is constantly dogged by corruption.

The lack of a competitive two-party system in Philadelphia hurts every taxpayer regardless of political affiliation. With no real challengers, elected officials focus on preserving their self-interest and catering to those who are connected to City Hall rather than serving the broader public.

Until the GOP ever gets its act together, voters are trapped in a one-horse town — except the horse is a Democratic donkey.