That makes six publicly declared candidates, including Diane Finley, Rob Nicholson and Erin O'Toole from Ontario, and Candice Bergen from Manitoba.
Ambrose said she has spent the last few days calling colleagues, and emphasizing a few key points about herself. She noted that she has held eight cabinet posts since 2006, and developed a reputation for civility in the House of Commons.
"A respectful tone and civil tone and working across the floor with other parties is something our members would welcome, that our caucus would welcome, and that Canadians would welcome as well,'' Ambrose said in an interview.
Lake, who served as a parliamentary secretary in the last Parliament and was first elected in 2006, linked the party's demotion to opposition status on Oct. 19 to a failure to communicate the Conservative record.
"In my riding, it was a message that was heard. For whatever reason, in other parts of the country it wasn't,'' he said in an interview.
"I think we have to rely on the 99 people that we have that are coming back here to give some real hard thought to that and develop a strategy that helps us to get our message through.''
Lake didn't go into specifics, but in a note to colleagues declaring his intention to run, he pulled no punches in denouncing the party's campaign efforts.
"Our major communications tools literally contained no substance, despite having a leader whose greatest brand strength was substance,'' he wrote.
"In the final two weeks, while the Liberals ran the ads we should have been running, Conservative ads — in their tone —were easy to confuse with life insurance and pre-planned funeral ads.''
Both Ambrose and Lake say outreach in Quebec in particular will be important — there are now 12 Quebec Conservative MPs, up from five in 2011.
Lake said he speaks some French, but isn't proficient, though has travelled through Quebec several times in his past parliamentary roles and says he has good relationships there.
Ambrose, who notes she is able to speak French (in addition to Spanish and Portuguese), said she intends on spending time in Quebec as part of cross-country travel she would undertake as interim leader to rally supporters and to raise money.
"We've got make sure we're prepared to welcome the next leader with money in the bank and a rejuvenated volunteer base, and a caucus that is united and reinvigorated and empowered, so that when a leader takes over, things are in the best possible position to take us into the next election and continue to take on Justin Trudeau in the Commons,'' she said.
Lake said he'll also be seeking to combine the energy of newly elected MPs with the wisdom of the party's veterans to build a renewed Conservative team.
"I think that as soon as Parliament resumes we want to create a level of energy that is going to carry through to a leadership race and beyond and build some momentum,'' he said.
"We've got a long game to play here and we have a real opportunity for people to gain some valuable experience.''
Ambrose is taking the position that senators should be allowed to cast a ballot in the interim leadership race, while Lake said he thinks the answer to that question is best decided when caucus meets Thursday.
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