The "desire to see change" and frustration at political deadlock have been hailed as reasons behind the Alliance Party's electoral success.
Speaking at the party's annual conference on Saturday deputy leader Stephen Farry told delegates Northern Ireland was changing "more quickly than many people appreciate".
The North Down MP delivered the keynote speech in the absence of Naomi Long.
The party leader was unable to attend after contracting a chest infection.
Speaking at Belfast's Stormont Hotel Mr Farry, who was elected to Parliament in December's general election, said the past year was Alliance's "most successful electoral year to date".
He said the party's success in the local elections exceeded their "wildest expectations" with "an incredible 53 councillors returned from an existing base in the low 30s".
Analysis by BBC News NI political editor Mark Devenport
Alliance hoped their 50th anniversary conference would be a celebration of their recent election successes.
Instead it will probably be remembered as the gathering the leader had to stay away from due to illness.
Stephen Farry delivered the central speech with his customary clarity.
But he's not blessed with some of the crowd-pleasing attributes of his absent leader.
Mr Farry put Alliance's surge down to its opposition to Brexit, frustration at the Stormont deadlock and the changing nature of Northern Ireland society.
Looking to the future, the North Down MP doesn't see a case for a border poll.
But he believes Alliance can engage with confidence in the debate about the constitutional future.
His assurance that Alliance can take part in a "rational and evidence-based discussion" without having to take sides or declare a particular preferred outcome may be tested over the coming months.
"With a few more votes in the right places, we could have won even more seats," he added.
"We are now players in councils right across Northern Ireland."
The deputy leader said the council elections were " just the warm-up act for the Alliance surge", going on to describe Naomi Long's success in the European elections as "quite stunning".
Mr Farry described vote increases in December's general election as "spectacular".
"I previously described Alliance as the fifth party in a four-party system," he said.
"We have now made the historic breakthrough to be the third party in share of the vote."
Mr Farry said the Alliance Party had "broken the glass ceiling" and could now win anywhere in Northern Ireland.
Turning to Brexit, which the party opposed, he added the UK was "turning its back on its biggest and most important neighbours for the pipe dream of a global Britain".
"All the time failing to acknowledge that it is through the EU that the UK can best project soft power and expand international trade and without selling off the NHS or betraying our farmers and agrifood sector," he said.
"And not undermining employment rights or putting our environment further at risk."
Mr Farry stressed his party did not want to see any borders or friction "anywhere in these islands".
On the restoration of the Stormont institutions, the North Down MP said while the New Decade New Approach deal "was not perfect" it was "a necessary starting point".
On the challenges ahead, Mr Farry identified three key areas for the party to focus on:
Mr Farry concluded his speech saying Alliance played a "crucial and constructive role in transforming Northern Ireland" but added "there is so much more to do".
"The next few years are set to a rollercoaster, but our vision and values will be instrumental in steering this society to a secure and better future," he said.