Achi news desk-
He also said the opposition had made a tactical error by allowing the SNP’s “biggest hitter” to take over.
READ MORE: John Swinney is about to become SNP leader and First Minister
Mr Brown’s comments came before nominations closed in the leadership contest.
Over the weekend, there was speculation that activist Graeme McCormick could table a motion after he secured the necessary number of nominations from members.
But late on Sunday he told Bylines Scotland he would be back out of the race after a “long and fruitful” chat with Mr Swinney.
Speaking to the BBC’s Good Morning Scotland radio programme, Mr Brown said it was important to respect the SNP’s democratic processes.
He said: “The field seems to be cleaning up a bit and it looks like John Swinney is the only nominee.”
Mr Brown described Mr Swinney as the “biggest hitter in the SNP” who would “pretty much scare” unionist parties.
He continued: “I also understand over the weekend, of course, we’ve got people out canvassing and they’ve already reported a positive increase in turnout coming back from those canvassing sessions.
“So there is an immediate boost from the discussions that John Swinney has had first of all with Kate Forbes and, it seems now, with Graeme McCormick.”
READ MORE: Changes on the way for BBC Scotland as decisions emerge for Swinney
It is expected that Mr Swinney could become Prime Minister as soon as tomorrow. Mr Yousaf will chair his last cabinet before tendering his resignation to the King.
MLAs will then vote for the new First Minister in the afternoon.
Mr Swinney would then have to swear three oaths in office at the Court of Session in Edinburgh before officially becoming prime minister.
Mr Swinney’s move to Bute House comes as the poll predicts a turbulent time for the SNP.
A survey by Norstat – formerly known as Panelbase – found that support for independence remains largely unchanged, but that Labor is about to overtake the SNP in Westminster and Holyrood.
According to the Sunday Times poll, the SNP would win 29% of the vote, while Labor would take 34%.
Professor Sir John Curtice told the paper that Mr Swinney’s party would hold just 15 of its 43 seats with Scottish Labor winning 28.
Responding to Mr Brown’s interview, the Chairman of the Scottish Conservatives, Craig Hoy, said: “Scots are desperate for the next leader of the SNP to focus on the issues that matter to them such as cutting NHS waiting times, restoring standards in our schools and growing our economy.
“Instead, John Swinney is going to prioritize governing in the interests of the SNP, rather than the interests of the country.
“Keith Brown has the brazen neck to say that his next boss will build on the successes of Humza Yousaf’s leadership, when his tenure was characterized by scandals, endless U-turns and a failure to focus on Scotland’s real priorities.
“In key seats across Scotland in the General Election, only the Scottish Conservatives can beat the SNP, put a stop to their independence obsession and get the focus on the issues that really matter.”
