Microsoft (NASDAQ:MSFT)Bing has always been an also-ran in the search engine market.

It is not that Bing has been a low-ranking player -- the No. 2 choice in the United States for a number of years. Instead, the problem is that Google (NASDAQ:GOOG) (NASDAQ:GOOGL) has been so dominant that second place has hardly mattered.

This has not been a Coca-Cola vs. Pepsi battle with a clear market leader and a serious challenger. Instead, it has been more like Coke versus Royal Crown Cola, where one company has such a large lead that the rival is more of a punchline that a real contender.

It is possible, however, that those days are over, as Bing has gained more than enough market share to be taken seriously.

What has Bing accomplished?
The Microsoft search engine has managed to crack a 20% share of the U.S. desktop market for home and work locations. Google still leads the way with 64.4%, but the search giant dropped slightly, while Bing gained. Specifically, Google fell 0.1% with Bing adding 0.3%.

That may be only a tiny gain for Microsoft, but it is the first time Bing has moved above the 20% market share level, according to USA Today. The jump also means that "Bing's share of U.S. Internet search is bigger than the market share of Apple's Mac in the computer market," the paper reported.

It is also worth noting that Bing powers the results for Yahoo! -- a recently renewed arrangement -- giving Microsoft nearly one-third of all searches. Google is still dominant, but Bing has become a major player in its own right.

comScore Explicit Core Search Share Report* (Desktop Only)
March 2015 vs. February 2015 (Total U.S. -- Desktop Home and Work Locations)

Core Search EntityShare (%) Feb. 2015Share (%) March 2015Point Change
Total Explicit Core Search 100% 100% 0
Google Sites 64.5% 64.4% (0.1)
Microsoft Sites 19.8% 20.1% 0.3
Yahoo! Sites 12.8% 12.7% (0.1)
Ask Network 1.8% 1.8% 0.0
AOL 1.1% 1.1% 0.0

Source: comScore qSearch.
*"Explicit Core Search" excludes contextually driven searches that do not reflect specific user intent to interact with the search results.

How is Microsoft doing this?
Bing has been leveraging its Rewards program to give people incentive to use its search engine. Simply conducting searches through Bing lets users earn points that can be turned in for gift certificates at popular retailers. That is a strategy likely to appeal to millennials, who have grown up with games powered by that model.

"The program -- the Internet search version of a frequent-flier program -- has been helpful in breaking Google's de facto grip on search with users looking to get a piece of their own online revenue," wrote USA Today.

It is a novel strategy that makes sense -- while Google is the dominant player, there is little difference in the results between either search engine. Giving people a reason to use one over the other (beyond whatever the default choice is set on your browser) could send people toward Bing.

How big a deal is this?
It is a victory for Microsoft but only a minor one. Making gains in desktop search is nice, but Google still dominates when it comes to mobile, with a 93% share according to NetMarketShare. That market is going to be much harder for Bing to crack, because the search engine has little to no presence on the Android and Apple iOS devices that control the tablet and smartphone worlds.

Desktop gains are something for Microsoft to celebrate, and the numbers could become stronger if Windows 10 proves more popular than the beleaguered predecessor it is replacing. If that happens, more people could upgrade to new Windows computers with Bing as the default search engine.

Microsoft could also make gains in mobile if Win10 proves to be popular, and the fledgling market for WIndows Phone and Windows-powered tablets grows.

Bing is far from toppling Gooogle, but Microsoft has shown that it has the potential to make this a real race. The underdog is in a stronger position than it has ever held before.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.