Margaret Curran has been named as the Labour candidate in the Glasgow East Westminster by-election.
The MSP for Glasgow Baillieston will launch her campaign on Tuesday. She was chosen after frontrunner, George Ryan, pulled out of the race last week.
Campaigning on Monday also saw the SNP call for action on fuel bills. The Tories promised to tackle social decay.
The Liberal Democrats will formally launch their campaign on Tuesday as will the Scottish Socialist Party.
The 24 July by-election was triggered by Labour MP David Marshall's resignation on health grounds.
Labour was expected to name George Ryan as its candidate on Friday night but he failed to turn up for a selection meeting. He later cited family reasons for pulling out.
Ms Curran emerged as the new frontrunner over the weekend amid speculation that several other party figures had turned down the chance to stand.
She is currently Labour's health and wellbeing spokeswoman at Holyrood, having been first elected in 1999 and returned in 2003 and 2007.
She has indicated that if she wins Glasgow East she will continue as an MSP and MP for the immediate future.
Speaking as she stepped out of the selection meeting, Ms Curran said she was in politics to fight poverty and stand up for the people of the east end.
She said: "That's what I've done all my life, and what I promise to keep on doing.
"Let me be clear: Labour's fightback starts right here, right now."
The constituency was one of the safest Labour seats in Scotland at the last election, with a majority of more than 13,500 over the SNP.
It also had the highest Labour vote share in the city at the General Election.
Other candidates declared include Glasgow councillor John Mason for the SNP, university worker Davena Rankin for the Conservatives, maths teacher Ian Robertson for the Liberal Democrats, retired GP Eileen Duke for the Scottish Greens, former MSP Frances Curran for the Scottish Socialist Party and council worker Tricia McLeish for Solidarity.