The rally comes as a new poll suggests the upstart Senators are gaining ground in public support on the Toronto Maple Leafs and Montreal Canadiens, this country's most storied hockey franchises.
But with the Senators set to begin the best-of-seven Cup final against the Anaheim Ducks on Monday night in southern California, it's clear not all hockey fans are ready to accept the notion of a team from the national capital as "Canada's team."
With the Senators flooding the airwaves as the lone Canadian franchise at the dance, a survey by Decima Research last weekend suggests most Canadians still see the Leafs as the team that most represents the country.
Overall, 24 per cent of the just over 1,000 people surveyed between May 17 and 20 named Toronto as Canada's team, while 22 per cent picked the Habs and just 15 per cent chose the Senators.
Among the nearly one-quarter of respondents who identified themselves as avid hockey fans, 27 per cent picked the Leafs, even though they failed to make the playoffs and have been golfing for a month.
For some Leafs fans, the survey result comes as no surprise.
"All of this chatter about the Senator's being 'Canada's Team' is clearly a fallacious argumentum ad populum, being promoted by knuckle-dragging, low-brow types attempting to generate false allegiances," one Leafs die-hard emailed The Canadian Press from Fort Francis, Ont.
"Most long-suffering Leaf fans are patient enough to decline the free ride on this bandwagon. What we lack in pride, is made up for in terms of dignity (and apparently popular support)."
NHL hockey has fallen out of the top 30 rated shows in the all-important Toronto market, and overall ratings for CBC's Hockey Night in Canada were down 15 per per cent in the Ottawa-Buffalo Eastern Conference final compared to last year's western final that featured the Edmonton Oilers.
Even the reigning Miss Canada, Inga Skaya, was photographed this week wearing a Toronto Maple Leafs sweater as part of her "national" costume at the Miss Universe Pageant in Mexico City.
For the 15-year-old modern Senators franchise, winning converts has been a long, hard slog but one the Stanley Cup appearance should give momentum.
Among those hard-core hockey fans, Decima found close to 26 per cent picked the Senators as Canada's team, while 23 per cent chose the Canadiens. That put Toronto, Ottawa and Montreal nearly even among die-hards, considering the poll's margin of error of 3.1 per cent, 19 times in 20.
Cape Breton native Laura Drover was among the 10,000 to 15,000 who thronged into a square around Ottawa City Hall on Thursday, and she conceded she's a late Senators convert.
"Maybe when it was the original six (Canadian teams) I had my Maple Leaf gloves and shin pads, but now it's all Sens all the way," she said, carrying a sign that read "Hunting Season Open for Duck."
Decima CEO Bruce Anderson said that considering the long hockey history Ottawa must overcome, the poll results are quite strong.
"While the rivalry between the Maple Leafs and the Canadiens has been one of the longest running and highest profile story lines in NHL (history). . . the results also show that the Senators have established a claim to a place for themselves in the debate about which is 'Canada's team' of the future, especially among avid followers of the game," said Anderson.
"The possibility of the Senators bringing the Stanley Cup back to Canada for the first time in more than a decade has won the enthusiastic support of millions of Canadians."
Over the past decade, Ottawa watched as its young team became an NHL powerhouse but was denied a Stanley Cup appearance by various playoff disasters - including four times at the hands of the Maple Leafs.
Those frustrating days are over, said Ottawa Mayor Larry O'Brien, who encouraged hockey fans across the country to rally behind the Senators. No Canadian team has won the cup since Montreal in 1993.
"We've paid our dues," O'Brien said after the rally.
"We now have a world class hockey team, we're now a world class city . . . and I think it's all just coming together."
According to Decima, many Canadians agree.
Nearly half of those polled thought it likely the Senators will bring home Lord Stanley's mug, although only 14 per cent consider it a sure thing. Among avid hockey fans, 88 per cent said they think the Senators will win the series.
Nine per cent think they'll lose .
Support for individual teams varies from province to province.
Not surprisingly, 58 per cent of those polled in Quebec picked the Habs as their favourite Canadian team, compared to the Senators at 13 per cent. No other team registered more than one per cent support.
In Ontario, 47 per cent chose the Leafs - more than double the 22 per cent support shown for the Sens, even though Ottawa is also an Ontario team. Another eight per cent of those polled in Ontario picked the Canadiens, while no other team registered more than one per cent support in Ontario.