"Two individuals who I have admired from a distance today have joined the Progressive Conservative caucus," Prentice, flanked by Towle and Ian Donovan, told a legislature news conference.
"I'm pleased and humbled by their support. I've admired the work ethic and the integrity of both of these individuals."
Prentice said his caucus had voted unanimously to admit the pair. He said he did not promise them anything or entice them in any way to cross the floor.
The two rookie members of the legislature looked downcast during the news conference, with Towle on the verge of tears.
Towle, the member for Innisfail-Sylvan Lake, had risen quickly to become one of the key lieutenants to Wildrose Leader Danielle Smith and a sharp critic of the Tories on social policy and the treatment of seniors.
She said she had been weighing her decision for more than a week and decided Sunday it was time to go.
"It's incredibly difficult. I consider most of my caucus mates my friends, but I felt I had done all that I could in the role I was in," said Towle.
She said she has been dismayed by the route the Wildrose was taking.
"We are a party of free votes, however our membership was deciding how I as an MLA was expected to vote, and that caused me great conflict," she said.
"My constituents were coming to me asking me to give this government and Mr. Prentice a chance, and felt I could do more with them than against them — and I heard that message."
Donovan said his constituents in Little Bow also told him to look at following Prentice, and he listened.
"I'm impressed with the new leadership," he said.
"For my constituents, I think I can do the best from the inside, making decisions around the table with the governing party."
Donovan said he was disillusioned with Smith, who said recently if the Wildrose does not win the 2016 election, she will quit as leader.
"I respect Danielle Smith to the utmost, (but) it's hard to follow somebody when they say they're not sure they're going to lead the team if they don't win the next game," he said.
Smith, in a news conference, compared Donovan and Towle with Wildrose members Rob Anderson and Heather Forsyth.
Anderson and Forsyth crossed the floor in 2010 to the Wildrose from the PCs.
"Rob and Heather crossed the floor from government to opposition because of principle," said Smith.
"They gave up the perks of power to serve Albertans, not for personal gain, but because they want to put Albertans first. Today we saw the opposite."
Smith refused to take questions from reporters.
Towle and Donovan will take their places on the government side of the legislature chamber on Tuesday.
The PCs now have 63 members in the 87-seat legislature. There are now 14 Wildrose members, five Liberals, four NDP and one Independent.
Monday's announcement was the latest body blow to a party that has been on the ropes since it lost four byelections to Prentice on Oct. 27.
The byelection losses set off a cascading train wreck of changes and decisions.
Smith and her team were blamed for pursuing the wrong strategy in the byelections, trying to paint Prentice with the same brush of scandal as former premier Alison Redford.
In response, Smith shook up her communications and political staff. Caucus member Joe Anglin then quit ahead of being fired by the caucus. Smith accused Anglin of undermining caucus for a year by secretly taping them.
Anglin denied it, and Smith admitted she had no proof.
Things worsened at the Wildrose annual general meeting 10 days ago. Smith, in her keynote speech, accused the media of slanting its reporting to build the narrative of a negative, angry Wildrose party.
A day later, Smith was out of the room when party members voted to reject putting into policy a statement they passed a year earlier promising to respect the rights of minority groups, including gays and lesbians.
While Smith said the party still endorses fairness for all, the vote re-ignited simmering criticism that the rural-based party is bigoted and anti-gay.
Days later, Calgary riding executive member Terry Lo quit, saying the party is run by a cabal of members who are against gays and ethnics.
Earlier Monday, Anderson announced that despite the rejection of the specific rights policy by the membership, the caucus will follow it anyway.
Political scientist Duane Bratt said the defections may be mortal wounds to Smith, as they were to former Tory premiers Ed Stelmach and Redford.
Political disagreement is one thing, said Bratt, but when MLAs vote with their feet, it's over, he said.
"I don't know if she can (stay on as leader)," said Bratt, with Mount Royal University in Calgary.
Anglin said he expects there will be more defections.
"I know of five, total, counting these two," he said. "Are there more than that? I suspect people who have not spoken to me have thought about it, absolutely."
-- with files from CHED
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