The fact that Mayor Marty Walsh will face a credible challenger in 2017 shouldn’t be such big news. That the entry of City Councilor Tito Jackson seems so notable is an uncomfortable commentary on Boston’s political landscape, and the way the deck is still stacked against challengers.

Jackson, who formally declared his candidacy at a well-attended rally outside Haley House in Roxbury on Thursday, will be fighting against decades of tradition in his bid to oust Walsh. No incumbent mayor has lost since 1949 — and that mayor, James Michael Curley, had been convicted of a federal crime during his term. Walsh also starts with a massive cash advantage: He has $3.6 million in his campaign account, compared with $65,000 for Jackson.

It’s not necessary to oppose Walsh to see something wrong with this picture. Contested elections are the essence of democracy, but, judging by the collective actions and inactions of politicians, donors, and activists, Boston prefers to avoid them. Why?

Simply by entering the race, Jackson opens the door for a discussion of Walsh’s record (and Jackson’s, of course). Jackson wants to focus on education and affordable housing, and clearly plans to take Walsh to task for his backing of the city’s ill-fated Olympics bid. At his announcement rally, Jackson previewed what may turn into his campaign themes, criticizing the mayor’s use of tax incentives to lure General Electric and his backing for the failed IndyCar race. If Jackson sticks to such policy disagreements, it should lead to healthy debates this fall over the city’s future.

And they’ll be even healthier if more candidates join the race — not just for mayor, but also for city council. With a few notable exceptions, councilors almost never face serious opponents. It’s early, but there are few indications of competitive council races so far.

One way to break the cycle of noncompetitive elections would be to reform campaign finance laws to make it more difficult for candidates to amass such huge war chests like Walsh’s. Campaign accounts shouldn’t carry over from campaign to campaign — it means that each uncontested election only breeds another one. “Entrenched’’ politicians get that way when they can fortify their position with an ever-growing wall of money.

But the best way to improve elections in Boston is to do what Jackson is doing: run in them. Let’s hope others follow his example.