Former Gov. Brian Schweitzer is widely expected to run for Montana’s open Senate seat — the only question is when.

State legislators and operatives had heard he was preparing to announce his bid on Tuesday, but that day came and went without a peep from the populist Democrat.

Another likely option? The state party is holding a convention in Lewiston on Friday and Saturday, offering Schweitzer a room already packed with party faithful. At least one local Democratic official speculated he could make an announcement then.

“I think that there’s probably a 99.9 percent likelihood that he will [run],” said state Senate Minority Whip Robyn Driscoll, a Democrat supportive of Schweitzer. “Rumors have been floating around for a few weeks about when the announcement would be made. … We are having our Democratic convention this weekend, and so I’ll be looking for an announcement maybe then.”

Attempts to reach Schweitzer and his team about the delay were unsuccessful, and Schweitzer — who is known for personally calling reporters — did not return a call to his cellphone.

Republicans plan to compete regardless of whether Schweitzer is in the race, but potential candidates appear to be awaiting Schweitzer’s decision. Former state Sen. Corey Stapleton and state Rep. Champ Edmunds are the only two Republicans in the race so far.

Rep. Steve Daines is seriously considering it and would have plenty of establishment support. GOP senators have contributed to his House campaign account in an apparent attempt to recruit him, Bloomberg News reported.

“I know he’s been talking about it,” state Senate Majority Leader Art Wittich, a Republican, said of Daines. “But there are a couple of people interested in getting in the race who haven’t announced yet.”

Schweitzer may not be officially in yet, but the national vetting process has already begun. Republicans have been preparing for his candidacy for some time, building an opposition research operation to sift through his eight years as governor. And The Associated Press looked into connections between Schweitzer and an outside group in a story last week.

Over his eight years as governor, Schweitzer’s gregarious style attracted plenty of positive attention, but he also often rubbed people in both parties the wrong way. That includes those in the congressional delegation. In preparation for a bid, he’s reached out to the political apparatus of retiring Sen. Max Baucus — with whom he has a frosty relationship — to extend an olive branch, several sources said last month.

But the former governor’s ability to build support among voters across the political spectrum has Democrats excited about his potential, Driscoll said. State Democrats believe he provides the party with its best chance to hold the Baucus seat in this Republican-leaning state. Democratic Sen. Jon Tester won in 2012 despite a double-digit loss in the state by President Barack Obama.

“I’ve heard rumors for months and months now about him deciding to announce or deciding to run,” state House Minority Caucus Leader Bryce Bennett, a Democrat, said. “I don’t know what his decision is, but I can certainly say that I hope he decides to run and to announce soon. We’re excited for him.”

The race is rated a Tossup by Rothenberg Political Report/Roll Call.